Optical pickup device

ABSTRACT

An optical pickup device has a single light beam path in which at least one or either of a plurality of kinds of light beams (different from each other in, for example, wavelength) for respective recording densities and/or recording-medium-thicknesses proceeds toward a surface of an optical recording medium and proceeds to a light beam detector after being reflected by the surface.

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT

The present invention relates to an optical pickup for recordinginformation onto an optical recording medium and/or reading out theinformation from the optical recording medium.

In the prior art, when information needs to be recorded onto a pluralityof optical recording media different in recording density and/ormedium-thickness from each other and/or to be read out from thedifferent optical recording media, a plurality of optical systems eachof which includes a light beam source, a collimator, a light beamsplitter, a quarter-wave plate, and an objective lens for respectiverecording density and/or medium-thickness are used.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an optical pickupdevice for recording media having recording densities and/orrecording-medium-thicknesses that are different from each other, whereina size of the optical pickup device is minimized.

An optical pickup device according to the present invention has a singlelight beam path in which at least one or either of a plurality of kindsof light beams (different from each other in, for example, wavelength)for the respective recording densities and/orrecording-media-thicknesses proceeds toward a surface of an opticalrecording medium and proceeds to a light beam detector after beingreflected by the surface.

Since the at least one or either of the plurality of kinds of lightbeams proceeds in the single light beam path in opposite directions, inother words, the single light beam path is used to pass the plurality ofkinds of light beams in the opposite directions, a structure and volumebetween the optical recording medium and light beam emitting elementsmay be small to minimize the size of the optical pickup device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section illustrating a configuration of packaging ofan optical pickup and an optical path of a first embodiment according tothe present invention;

FIG. 2 is a cross section of a peripheral portion of light sources ofthe first embodiment according to the present invention;

FIG. 3 is a cross section of a peripheral portion of light sources of anembodiment which is not according to the present invention;

FIG. 4 is a diagram illustrating a relationship between a luminous pointand a collimating lens of the first embodiment according to the presentinvention;

FIG. 5 is a diagram illustrating a relationship between a wavefrontaberration amount and a distance ratio depending on a shift amount of acondenser of the first embodiment according to the present invention;

FIG. 6 is a diagram illustrating a relationship between a luminous pointin a finite optical system and the condenser of the first embodimentaccording to the present invention;

FIG. 7 is a cross section of an integrated optical head of a secondembodiment according to the present invention;

FIG. 8 is an enlarged view of a neighborhood of light sources of thesecond embodiment according to the present invention;

FIG. 9 is an enlarged view of a neighborhood of the light sources of thesecond embodiment according to the present invention;

FIG. 10 is an enlarged view of a neighborhood of the light sources ofthe second embodiment according to the present invention;

FIG. 11 is a diagram illustrating a relationship between a luminouspoint in an infinite optical system and a collimating lens of the secondembodiment according to the present invention;

FIG. 12 is a diagram illustrating a relationship between a wavefrontaberration amount in light and a distance ratio depending on a presenceor absence of a shift of a condenser of the second embodiment accordingto the present invention;

FIG. 13 is a cross section of an integrated optical head of a thirdembodiment according to the present invention;

FIG. 14 is a cross section of an optical system of the third embodimentaccording to the present invention;

FIG. 15 is a cross section of a diffusion angle conversion means of thethird embodiment according to the present invention;

FIG. 16 is a diagram illustrating an arrangement of a light receivingmeans of the third embodiment according to the present invention;

FIG. 17 is a perspective view of a peripheral portion of a light sourcemounting portion of the third embodiment according to the presentinvention;

FIG. 18 is a cross section of the peripheral portion of the light sourcemounting portion of the third embodiment according to the presentinvention;

FIG. 19 is a diagram illustrating a relationship between a lens shiftamount and a wavefront aberration amount depending on a presence orabsence of a color aberration correcting means of the first embodimentaccording to the present invention; and

FIG. 20 is a cross section of a conventional optical pickup.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[First Embodiment]

At the outset, a first embodiment of the present invention will bedescribed below with reference to the accompanying drawings.

Referring to FIG. 1, there is shown a cross section of a configurationof an optical pickup and an optical path of the first embodimentaccording to the present invention. In FIG. 1, a dotted line representsan optical path for reproducing a low-density optical disk and a solidline represents an optical path for reproducing a high-density opticaldisk.

In FIG. 1, a first package 1 comprises a light source 2 for emittinglight for a high-density optical disk 18, a substrate portion 1 a onwhich a light receiving means 3 or the like are mounted to receive lightreflected by the high-density optical disk 18, and a sidewall portion 1b arranged so as to enclose these members. The substrate portion 1 a andthe sidewall portion 1 b and others can be formed either integrally orseparately. If they are integrally formed, an assembly process can besimplified so as to increase the productivity. As materials of the firstpackage 1, there are metal, resin, and ceramic. Particularly, it ispreferable to use the metal or ceramic in these since the heat generatedin the light source 2 can be favorably discharged.

Further in the metal materials, it is preferable to use metal materialssuch as Cu, Al, or Fe alloy materials such as FeNi alloy or FeNiCo alloyhaving high thermal conductivity. This is because these materials arelow-cost and have high heat dissipation effects, in addition to havingan effect of a magnetic shield which cuts off noises such aselectromagnetic waves from a high-frequency superposition circuit or thelike. In these materials, particularly Fe, FeNi alloy, and FeNiCo alloy,have lower thermal resistance and favorable heat dissipation, so thatthey can dissipate efficiently to the outside the heat which isgenerated in the light source 2. Additionally, these materials arelow-cost, and therefore it becomes possible to provide an optical pickupdevice at a low price.

Furthermore, the first package 1 discharges heat generated by the lightsource 2 to the outside by making the substrate portion 1 a and, ifnecessary, the sidewall portion 1 b, in contact with a carriage having agreat thermal capacity. Accordingly, as an area of the substrate portion1 a in contact with the carriage becomes larger, the package 1 obtainsmore favorable heat dissipation effects.

Still further, in the substrate portion 1 a, there are providedterminals 1 c for supplying power to the light source 2 and fortransmitting electric signals from the light receiving means 3 to anarithmetic circuit. These terminals 1 c can be either pin-typed orprinted-typed. In this embodiment, particularly pin-typed terminals 1 cwill be described below.

The terminals 1 c are inserted into a plurality of holes on thesubstrate portion 1 a without being electrically connected to thesubstrate portion 1 a made of metal material. For the materials of theterminals 1 c, it is preferable to use FeNiCo, FeNi, FeCr or otheralloy.

As means of interrupting the electrical connection between the substrateportion 1 a and the terminals 1 c, preferably an insulating coating isput on portions between respective terminals 1 c and substrate portion 1a in the holes, and further preferably, the coating is closed so thatthe air will not penetrate from these portions. As materials satisfyingthese requirements, it is preferable to use materials which are bothinsulating and impermeable such as with a hermetic seal. Particularly,it is preferable to use a hermetic seal of matched-sealing type orcompressed-sealing type. This is because these materials can be preparedvery easily for both of the insulating and hermetic effects in additionto being extremely low-cost, and therefore it is possible to simplify aprocess of mounting the terminals 1 c on the substrate portion 1 a andfurther to reduce a manufacturing cost of the optical pickup.

In addition, these types of hermetic seal can retain high hermetic andinsulating effects in a wide range of temperatures, and thereforereliability of the optical pickup can be improved and a shape of theterminals can be deformed relatively at will, whereby a degree offreedom of the design can be increased.

As the light source 2, it is preferable to use a light source which hasfavorable coherence, directivity, and condensing effects with a singlecolor, since a beam spot having an appropriate shape can be formedrelatively easily so as to restrain an occurrence of noises. It ispreferable to use various laser lights such as a solid, gas, orsemiconductor laser light as those satisfying these requirements.Particularly, the semiconductor laser is very small in size andeffective to make the optical pickup smaller easily, whereby it isoptimum as the light source 2.

In addition, preferably the light source 2 of the semiconductor laserhas preferably an 800 nm or lower oscillation wavelength, since it ispossible to make easily a beam spot, to which the light from the lightsource converges on a record medium, to have almost a size of a pitch ofa track formed on the record medium. Furthermore, if the oscillationwavelength of the light source 2 is 650 nm or lower, it is possible toform a beam spot which is so small that a record medium on whichextremely high-density information is recorded can be reproduced,whereby a mass storage means can be easily achieved, and particularly,it is preferably used as the light source 2 provided for reproduction ofrecords on a high-density optical disk.

If the light source 2 comprises a semiconductor laser, as materialswhich satisfy the requirement of the oscillation wavelength ofapproximately 800 nm or lower, there are AlGaInP, AlGaAs, ZnSe, and GaN;particularly AlGaAs is preferable in these chemical compound materialssince it has easy crystal growth characteristics, and therefore it iseffective to manufacture a semiconductor laser easily, which leads tohigh yield and high productivity. As materials which satisfy therequirement of the oscillation wavelength of 650 nm or lower, there areAlGaInP, ZnSe, and GaN. By using a semiconductor laser made of thesematerials as the light source 2, a diameter of the beam spot formed onthe record medium can be reduced further, which makes possible tofurther improve the recording density, and therefore it becomes possibleto reproduce a high-density optical disk.

In these materials, particularly AlGaAsP is preferable since it has astable performance for a long period, and therefore it makes it possibleto improve reliability of the light source 2.

In addition, preferably an output of the light source 2 is in a range ofapproximately 2 to 10 (mW) if it is dedicated to reproduction, since itmakes it possible to assure a sufficient quantity of light required forreproduction and to limit energy consumption to the minimum, and furtherto restrain the amount of heat which is discharged from the light source2. If the light source is used for both recording and reproduction, agreat amount of energy is required to change a status of a record layerat recording, and therefore at least 25 (mW) or greater output isneeded. If the output exceeds 50 mW, it becomes hard to dissipate theheat discharged from the light source 2 to the outside and therefore thelight source 2 and its peripheral portion have high temperature, wherebya life of the light source 2 is significantly reduced and, in the worstcase, the light source 2 may be destroyed. Accordingly, an electriccircuit may cause malfunction, the light source 2 itself may cause afluctuation of the wavelength which leads to a shift of the oscillationwavelength, or noises may be included in signals, by which thereliability of the optical pickup is significantly reduced, andtherefore an output exceeding the above-noted level is not preferable.

Next, an explanation will be made for a light source mounting portion150 on which the light source 2 is mounted.

The light source mounting portion 150 has a rectangular parallelepipedor plate shape with the light source 2 mounted on its top or sidesurface. The light source mounting portion 150, which is put on thesubstrate portion 1 a or the sidewall portion 1 b, dissipates the heatgenerated by the light source 2 in addition to holding the light source2.

For a joint between the light source mounting portion 150 and the lightsource 2, taking into consideration heat conductivity, it is preferableto use a method in which the top of the light source mounting portion150 is plated with a solder material such as Au—Sn before it is solderedat high temperature or a method in which Au—Sn, Sn—Ag, Sn—Sb, orSn—Pb—In foil (several μm to tens of μm in thickness) is contact-bondedat high temperature.

Unless the light source 2 is mounted almost in parallel with themounting surface of the light source mounting portion 150, it may causean aberration of an optical system or a reduction of a bondingefficiency. Therefore, preferably the light source 2 is mounted on thelight source mounting portion 150 at a predetermined position, at apredetermined height, and almost in parallel with the mounting surfacewhen it is bonded.

Furthermore, a plane of electrodes is placed on the top of the lightsource mounting portion 150 so that it is electrically connected to thebottom of the light source 2. The plane of electrodes is provided forsupplying power to the light source 2, and preferably a thin film of Auis used as a metal film composing the plane of electrodes from aviewpoint of conductivity and resistance properties.

The light source mounting portion 150 is preferably made of materialhaving high heat conductivity and a linear expansion coefficient closeto that of the light source 2 (approximately 6.5×10⁻⁶/° C.) from aviewpoint of the heat generated by the light source 2 or mounting on thelight source 2. Specifically, it is preferable to use materials having alinear expansion coefficient of 3 to 10×10⁻⁶/° C. and heat conductivityof 100 W/mK or greater, for example, AlN, SiC, T-cBN, Cu/W, Cu/Mo, orSi, and for example, diamond particularly when the light source 2 of ahigh output is used and the heat conductivity must be extremely high.

If the light source 2 and the light source mounting portion 150 have thesame or close values as the linear expansion coefficients, it ispossible to prevent an occurrence of distortion between the light source2 and the light source mounting portion 150, which makes it possible toprevent disadvantages that the mounted portion between the light source2 and the light source mounting portion 150 gets out of place or that acrack is made on the light source 2.

If they are out of the above range, however, a large distortion mayoccur between the light source 2 and the light source mounting portion150, which increases a possibility of causing problems that the mountedportion gets out of place between the light source 2 and the lightsource mounting portion 150 or that a crack is made on the light source2.

In addition, with the heat conductivity of the light source mountingportion 150 set as high as possible, the heat generated by the lightsource 2 can be efficiently dissipated to the outside.

If the heat conductivity is lower than the level described above,however, it becomes hard to dissipate the heat generated by the lightsource 2 to the outside, and therefore the temperature of the lightsource 2 is increased and the wavelength of the light emitted from thelight source 2 is shifted. As a result, a convergence position of thelight on the record medium changes minutely, whereby a lot of noiseelements are included in reproduced signals or whereby an output of thelight source 2 is decreased and a record reproducing operation on therecord medium cannot be normally performed. Further, the life of thelight source 2 is reduced, or in the worst case, the light source 2 maybe destroyed or other disadvantages can easily occur.

This embodiment uses AlN having very excellent characteristics in thesetwo aspects.

Furthermore, it is preferable to form thin films of Ti, Pt, and Au inthis order from the light source mounting portion 150 to the lightsource 2 on the top of the light source mounting potion 150 so that thelight source mounting portion has favorable bonding effects with thelight source 2. If Si is used as a material of the light source mountingportion 150, it is preferable to form an insulating layer such as Al₂O₃film or a surface oxidation film on the member surface before the Tilayer is formed.

Next, an arrangement of the light source mounting portion 150 on thesubstrate potion 1 a will be described below. Referring to FIG. 2, thereis shown a cross section of a peripheral portion of the light source inthe first embodiment according to the present invention.

On the substrate portion 1 a, a raised portion 151 having an almostrectangular parallelepiped shape is formed. By making a side portion 151a of the raised portion 151 in contact with a side portion 150 a of thelight source mounting portion 150, positioning of the light sourcemounting portion 150 can be performed. In other words, the light sourcemounting potion 150 is previously placed on a surface if of thesubstrate 1 a, and the light source mounting potion 150 is bonded to theside portion 151 a of the raised portion 151 which is preciselychamfered by means of a bonding material while being pressed on it.

With this configuration, the light source mounting portion 150 on whichthe light source 2 is mounted can be placed in a predetermined positionmore easily and precisely, whereby it becomes possible to achieve ahigh-performance optical pickup whose optical characteristics are lessdegraded by a deviation of the position of the light source 2.

Although the positioning of the light source mounting portion isperformed by using the raised portion in this embodiment, the sameeffect can be obtained by arranging a recess portion on the substrateportion.

As for the bonding material used for bonding between the light sourcemounting portion 150 and the substrate portion 1 a, it is preferable touse a metallic bonding material such as solder or an optical hardeningresin which is hardened by an ultraviolet light or a visible light sincethey have a bonding power exceeding a level of the required value.Particularly when using a metallic bonding material, it is preferable totake measures for obtaining favorable bonding effects such as previousplating with metal for the surface if of the substrate portion 1 a, theside 151 a of the raised portion 151, and the bottom 150 b or the side150 a of the light source mounting portion 150.

In addition, preferably an angular portion, which is formed by thebottom 150 b of the light source mounting portion 150 and the side 150 awhich is in contact with the raised portion 151, has a predeterminedradius (R) or has a corner whose sharp edge is removed.

This will be described with reference to the drawings. Referring to FIG.3, there is shown an enlarged view of a peripheral portion of the lightsource in an embodiment which is not according to the present invention.As shown in FIG. 3, in general, frequently the surface 1 f of thesubstrate 1 a does not cross at right angles precisely to the side 151 aof the raised portion 151. In this case, when the light source mountingportion 150 is pressed on the raised portion 151, the light sourcemounting portion 150 is inclined as shown in the drawing, which causes adeviation from a predetermined position of an optical axis of the lightemitted from the light source 2 mounted on the light source mountingportion 150, whereby a predetermined track of the record medium is notirradiated with the light. Therefore, precise recording nor reproductioncannot be performed.

Accordingly, in this embodiment, as shown in FIG. 2, there is provided aconfiguration in which the angular portion, which faces the raisedportion 151 of the light source mounting portion 150 and the substrateportion 1 a, is rounded (represented by a solid line in the drawing) orits sharp edge of the corner is removed (represented by a dotted line inthe drawing), so that the corner is not brought into contact with thenon-rectangular portion formed by the surface 1 f of the substrateportion 1 a and the side 150 a of the raised portion 151 or is adaptedto fit the non-rectangular portion.

With this configuration, even if the surface 1 f of the substrateportion 1 a does not cross at right angles to the side 151 a of theraised portion 151, the light source mounting portion 150 can be bondedwith the substrate portion 1 a in an accurate position, and therefore itbecomes possible to achieve an optical pickup having favorable recordreproduction characteristics without any deviation from a predeterminedposition of the optical axis of the light emitted from the light source2 mounted on the light source mounting portion 150.

Furthermore, preferably the light source 2 mounted on the light sourcemounting portion 150 is formed so as to face the raised portion 151, inother words, the raised portion 151 is formed in an extending directionof a backward emitting light 2 h from the light source 2. Explanationwill be made below for this description.

Since the raised portion 151 is used for precise positioning of thelight source mounting portion 150 as set forth above, it can beintrinsically in contact with any surface only if it is in contact withthe light source mounting portion 150. It is necessary, however, to takepreventive measures so as to inhibit the backward emitting light 2 hfrom the light source 2 from being incident upon the light receivingmeans or optical members as stray light. In this embodiment, thesemeasures are taken on the raised portion 151.

In this embodiment, the top 151 c of the raised portion 151 is inclinedrelative to an end surface 2 i on which a luminous point 2g of the lightsource 2 exists. On the top 151 c, a metallic or dielectric film havinga high reflectance is formed over the surface or partially so as toreflect the backward emitting light 2 h from the luminous point 2 g uponthe top 151 c non-perpendicularly. Preferably the angle of inclinationon the top 151 c of the raised portion 151 to the end surface 2 i is setaccording to an angle of diffusion of the light emitted from the lightsource 2.

With this configuration, the backward emitting light 2 h from the lightsource 2 can be favorably reflected in predetermined directions andpreferably it is possible to prevent the backward emitting light 2 hfrom being incident as a stray light on the optical members or lightreceiving means with being reflected or diffused inside the package 1.

Although the top 151 c of the raised portion 151 is formed so as to havea high reflectance, a high extinction modulus can be applied instead ofthe high reflectance. As a configuration for increasing the extinctionmodulus, there is a method of arranging an extinction film over thesurface of the top 151 c or on a part of it. As for the extinction film,a translucent glass or resin material, an Si or Ti film, or an Si filmand a Ti film is often used in a predetermined thickness.

Furthermore, preferably the film thickness of the extinction film ischanged according to the wavelength of the incident light. In thismanner, also with respect to light sources having various wavelengths,the extinction film can securely absorb the light from the respectivelight sources.

In the configuration in which the extinction film is used, most of theenergy of the absorbed light is converted to heat, and therefore it ispreferable to use a material having a favorable heat dissipation and ahigh heat conductivity as a material of the reflection member on whichthe extinction film is formed. By using these materials, it becomespossible to prevent an occurrence of disadvantages that a givenextinction effect cannot be obtained due to a change of an organizationof the extinction film caused by an increase of the temperature of thereflection member.

With this configuration, the light from the luminous point 2 g of thelight source 2 is absorbed on the top 151 c without being reflectedalmost at all, and therefore the light from the luminous point 2 ghardly impinges on the optical members as a stray light, whereby itbecomes possible to achieve an optical pickup having favorable signalcharacteristics.

Although the top 151 c of the raised portion 151 is inclined relative tothe end surface 2 i of the light source 2 in the example of the lightreflection type, it need not be inclined in this case.

In addition, the light source mounting portion 150 need not be placed ifthe light source 2 is formed on the same semiconductor substrate as forthe light receiving elements 3 or if the light source is directly placedon the substrate.

In the opening 1 d of the first package 1, there is a first opticalmember 5 which is bonded. The first optical member 5 serves as a guideof the light emitted from the light source 2 and reflected on the recordmedium to a predetermined position of the light receiving means 3. Inthis embodiment, an explanation will be made for a configuration inwhich the first optical member 5 has a plurality of inclined planes anda returning light is induced by using the optical elements formed onrespective inclined planes.

The first optical member 5 contains a first inclined plane 5 a and asecond inclined plane 5 b inside. Further, there are provided an opticalpath dividing means 6 comprising a half mirror and a polarizingseparation (polarization beam splitter) film on the first inclined plane5 a and a reflection means 7 for guiding the incident light to the lightreceiving means 3 on the second inclined plane 5 b. If data can berewritten into a high-density optical disk, the optical disk must beirradiated with extremely-high energy light, and therefore the lightemitted from the light source 2 must be guided to the optical disk asefficiently as possible. From this viewpoint, it is preferable to usethe optical path dividing means 6 made of a polarizing separationelement (polarization beam splitter), being combined with aquarter-wave(length) plate 4, since it improves an efficiency ofutilizing the light and makes it possible to use a plurality of types ofoptical disks for recording or reproduction. In addition, preferably itmakes it possible to restrain the amount of light emitted from the lightsource 2, whereby the life of the light source 2 can be prolonged andtherefore reliability of the optical disk unit can be improved.

The quarter-wavelength plate 4 serves as a converter of the lightincident with linear polarization to an elliptic polarization, and ifthe rotary direction of an elliptic polarization is reversed due to areflection on the record medium, the elliptic polarization is convertedto a linear polarization which crosses at right angles to the directionof the incident polarization described above.

In a position of the reflection means 7, it is preferable to arrange anoptical element which satisfies an object (for example, to form a focuserror signal with non-point aberration (astigmatism)). For example, if afocus error signal is formed in a knife edge method, there is providedan optical element which is capable of forming a knife edge in theposition of the reflection means 7, and if a focus error signal isobtained by using a non-point aberration (astigmatism) method, there isprovided an optical element which is capable of forming a non-pointaberration (astigmatism) in the position of the reflection means 7.Taking into consideration that these optical elements are formed in thefirst optical member 5, it is preferable to apply a configuration inwhich the optical elements are made of hologram since it makes theoptical member thinner than that with optical elements made of lens,whereby the space can be used more efficiently so as to make the firstoptical member 5 smaller and thinner easily.

In addition, preferably the first optical member 5 is formed in a shapeof a parallel planar plate as a whole since it is effective to preventan occurrence of aberration, whereby favorable reproduction signals orfocus tracking signals can be formed. Furthermore, preferably the firstoptical member 5 is mounted so that its top and bottom are preciselyperpendicular to the optical axis of the transmitted light since it iseffective to prevent an occurrence of the non-point aberration(astigmatism) and a degradation of reproduction signals caused by anunfocused spot.

As for materials of the first optical member 5, it is preferable to usematerials having a high light transmission such as glass or resin sinceit is effective to prevent a decrease of the quantity of light and adegradation of the optical characteristics of the light transmittedthrough the first optical member 5. Particularly, glass is preferable asa material of the first optical member 5 since it does not cause abirefringence and therefore the characteristics of the transmitted lightcan be favorably maintained. Furthermore, it is more preferable to useoptical glass having a low wavelength dispersion, in other words, a highAbbe's number such as a BK-7 since it is effective to prevent anoccurrence of an aberration of a spherical surface caused by afluctuation of a wavelength.

As for a method of forming the first optical member 5, it is preferableto use a method in which a plurality of die-shaped prisms containingoptical elements are linearly bonded or a method in which opticalelements are formed in predetermined positions of plate components andthen respective plate components are laminated to be cut out into agiven shape since these methods are useful to obtain favorableproductivity. Particularly the latter method is preferable since itmakes it possible to obtain both high productivity and high yield.

Although the first optical member 5 is directly bonded to the sidewall 1b of the first package 1 so as to close the opening 1 d arranged on thesidewall 1 b in this embodiment, the first package 1 can be spaced apartfrom the first optical member 5. By placing them separated from eachother, it becomes possible to adjust more precisely a distance betweenthe light source 2 and the first optical member 5 which becomes aproblem if the height of the package 1 is uneven, by which the opticalcharacteristics of the light guided to the light receiving means 3 bythe first optical member 5 can be favorably maintained, so that signalscan be detected accurately.

Next, referring to RIG. 1, a second package 8 comprises a substrateportion 8 a on which a light source 9 emitting light for a low-densityoptical disk and a light receiving means 10 are mounted and a sidewallportion 8 b arranged so as to enclose these members. The followingdescription of the second package 8 focuses on different points from thefirst package 1.

First, as materials of the second package 8, it is preferable to usemetal or ceramic in the same manner as for the first package 1 sincethey are effective to discharge favorably the heat generated by thelight source 9.

The heat conductivity of the material of the second package 8 ispreferably equivalent to or smaller than that of the material of thefirst package 1. This is because the light source 2 for the high-densityoptical disk 18 often has an output which is the same as or greater thanthat of the light source 9 for the low-density optical disk 19, andtherefore the amount of heat discharged from the light source 2 is thesame as or greater than that of the light source 9. This is because, ifthis package is configured so that the portions for holding the lightsources and for discharging heat have the same amount of heatconductivity if the amount of heat dissipation of the light source 2 isnot identical with that of the light source 9, a temperature of thelight source 2 becomes higher than that of the light source 9, whichcauses an unbalance in the operating conditions between the lightsources 2 and 9, and therefore in some cases the life of the lightsource 2 is greatly different from that of the light source 9, wherebythere is a possibility of causing disadvantages such as decreasingreliability of the optical pickup significantly.

With the heat conductivity of the material of the second package 8 beingequivalent to or smaller than the heat conductivity of the material ofthe first package 1, it becomes possible to reduce the possibility thatthe temperature of the light source 2 becomes higher than that of thelight source 9, and therefore differences of the operating conditionsbetween the light source 2 and the light source 9 can be reduced, sothat it is possible to prevent the above described disadvantages frombeing caused.

Preferably the first package 1 has a contact area different from an areawhere it is in contact with a carriage of the second package 8. Withthese different contact areas being provided, it becomes possible todischarge more heat per unit time due to the larger areas, and thereforea difference between the amounts of the generated heat can be favorablyresolved though the difference cannot be absorbed by a difference of theheat conductivity between respective packages. In this embodiment,particularly there is provided a large area where the first package 1 isin contact with the carriage.

Preferably the oscillation wavelength of the light source 9 is 800 nm orlower since a beam spot which is formed by the light emitted from thelight source and converging on the record medium can be easily adjustedto the similar size of the pitch of the track which is formed on therecord medium. Particularly the light source 9 is allowed to have anoscillation wavelength longer than that of the light source 2. Forexample, when a CD is reproduced, a beam spot of a sufficient size canbe formed on the low-density optical disk 19 with a wavelength of about780 nm.

Next, an explanation will be made for a light source mounting portion152 on which the light source 9 is to be mounted.

The light source mounting potion 152 is almost the same as the lightsource mounting portion 150 in its shape, mounting position, andfunctions, and therefore the explanation is omitted here. The amount ofheat generated by the light source 9, however, is not so great incomparison with that of the light source 2 in a lot of cases, andtherefore requirements of the characteristic values are not so severe asthose of the light source mounting portion 150. Therefore, the lightsource mounting portion 152 is preferably made of a material having alinear expansion coefficient close to that of the light source 9(approx. 6.5×10⁻⁶/° C.) and a heat conductivity which is ⅕ or greaterthan that of the light source mounting portion 150, taking intoconsideration an output ratio of the light source 2 to the light source9. Specifically, it is preferable to use a material having a linearexpansion coefficient of 3 to 10×10⁻⁶/° C. and a heat conductivity of 20W/mK or greater. For example, as these materials, there are Mo, Cu, Fe,FeNiCo alloy, or FeNi alloy in addition to the materials described asthe examples for the light source mounting portion 150. In thisembodiment, the light source mounting portion 152 is made of thematerials such as Cu, Mo, or the like, which are extremely low-cost incomparison with AlN which is the material of the light source mountingportion 150, and has relatively superior characteristics in the aboveaspects.

An area in which the light source mounting portion 152 is in contactwith the substrate portion 8 a or the sidewall portion 8 b is preferablysmaller than the area in which the light source mounting portion 150 isin contact with the substrate or sidewall portion. With thisconfiguration, it becomes possible to conduct the heat generated by thelight source 2 having a heat emitting amount generally greater than thatof the light source 9 to the substrate favorably in particular.Accordingly, also when using a semiconductor laser having a lowresistance to high temperatures, it is possible to prevent thetemperature in use of the light source 2 from being increased to a levelwhich is greatly higher than that of the light source 9, whereby thelife of the light source 2 is not clearly shorter than that of the lightsource 9 as a result, and therefore the life of the optical pickup canbe relatively prolonged and its reliability can be improved.

Furthermore, the light source mounting portion 152 is smaller than thelight source mounting portion 150 in the first package 1, and it will bedescribed below.

In a lot of cases, there is a difference between the required heatdissipation levels of the light source mounting potion 150 on which thelight source 2 is mounted and the light source mounting potion 152 onwhich the light source 9 is mounted. To cope with this difference, it isan effective method to apply different shapes to them.

In other words, the light source mounting portion 150 is formed in alarger size in comparison with the size of the light source mountingportion 152 to increase the heat capacity of the light source mountingportion 150, so that the heat generated by the light source 2 isefficiently conducted to the light source mounting portion 150.

With this configuration, the heat generated by the light source 2 can bedischarged through conduction to the light source mounting portion 150,and further heat dissipation caused by radiation from the surface of thelight source mounting portion 150 can be utilized at a greater ratio inaddition to the heat dissipation from the light source mounting portion150 through conduction to the substrate portion 1 a or the sidewallportion 1 b, whereby the heat from the light source 2 having a largeamount of heat emission can be discharged very efficiently.

Further, in this case, the amount of conducted heat of the light sourcemounting portion 150 is preferably greater than that of the light sourcemounting potion 152. With this configuration, it becomes possible todischarge the heat from the light source 2 having a greater output to anoutside more efficiently via the light source mounting portion 150.

Accordingly, it restrains a shift of a wavelength of the light emittedfrom the light source 2 which is caused by an increase of a temperatureof the light source 2 since the heat is accumulated around the lightsource 2. Furthermore, the increase of the temperature of the lightsource 2 can be efficiently restrained, and therefore it is possible toprevent the light source 2 from being degraded by the heat or from beingdestroyed, which improves the reliability of the optical pickup.

Although the light source mounting portions are discriminated byapplying different shapes to them in this embodiment, it is preferableto make a difference between them in their volumes since it affects theamounts of the accumulated heat most effectively.

In addition, with the surface area of the light source mounting portion150 being greater than the surface area of the light source mountingpotion 152, an amount of radiation heat from the surface of the lightsource mounting portion 150 can be increased. With an amount ofradiation heat per unit time from the light source mounting portion 150being greater than an amount of radiation heat per unit time from thelight source mounting portion 152, heat can be discharged to the outsideefficiently from the light source mounting portion 150 throughradiation, too, whereby a thermal load of the light source 2 can bereduced.

Although two light source packages are used in this embodiment, anynumber of light source packages can be used only if two or more packagesare used. At this point, preferably the physical properties of eachlight source mounting portion depends on an output of the light sourcemounted on the light source package.

As set forth hereinabove, with the physical properties (for example, aheat capacity, a size, a volume, a surface area, etc.) of the lightsource mounting portion 150 on which the light source 2 is mounted beingdifferent from the physical properties of the light source mountingportion 152 on which the light source 9 is mounted, it becomes possibleto discharge efficiently the heat from the light source 2 whose outputis high and which is likely to have a high temperature, and therefore itis possible to prevent a shift of the oscillation wavelength caused byan increase of the temperature of the light source 2 or to prevent thelight source 2 from being destroyed due to the heat.

In addition, the temperature of the light source 2 under the operationcan be almost the same as that of the light source 9, in other words,the operation is not performed with only one of them having a extremelyhigh temperature, and therefore there is not so much difference betweenthe lives of the light sources 2 and 9, whereby the optical pickup cansecure higher reliability without much variation of the life of theoptical pickup.

Although the second optical member 11 has almost the same configurationas for the first optical member 5, in some cases, there is a differenceof the optical elements formed on respective inclined planes betweenthem, and it will be described below. On a first inclined plane 11 a,there is provided an optical path dividing means 12 made of a halfmirror and a polarizing separation (polarization beam splitter) film,and on a second inclined plane 11 b, there is provided a reflectionmeans 13 for guiding an incident light to a light receiving means 10.

At this point, a signal detection method is different between ahigh-density optical disk and a low-density optical disk in a lot ofcases. Therefore, an arrangement of a light receiving section in thelight receiving means 10 is often different from that of the lightreceiving section of the light receiving means 3. Accordingly, if focuserror signals are formed by the reflection means 13 when a light fromthe optical disk is guided to the light receiving means 10, thereflection means 13 has preferably a shape different from that of thereflection means so as to form optimum signals for respective opticaldisks, whereby more precise signal forming and operation control can beachieved and it becomes possible to obtain a more reliable opticalpickup having less malfunctions.

An arrangement of the light source mounting portion 152 in the substrateportion 8 a is almost the same as that of the light source mountingpotion 150 in the substrate portion 1 a as shown in FIG. 2, and furtherin the same manner the light source 9 mounted on the light sourcemounting portion 152 is arranged so as to face a raised portion 153.Accordingly, an explanation of the arrangement is omitted here.

The oscillation wavelengths of the light sources 2 and 9 in thisembodiment, however, are different from each other since they are usedto cope with different record mediums; 630 to 660 nm for the lightsource 2 and 770 to 800 nm for the light source 9. Therefore, differentpoints caused by it will be described below.

Generally in the metallic or dielectric materials used for reflectinglight, a ratio of a reflected light to an incident light (a reflectance)or a ratio of an absorbed light to an incident light (an extinctionmodulus) often depends on a wavelength of the incident light, in otherwords, there is a dependence of the reflectance on the wavelength in alot of cases. Accordingly, if the lights from the light sources 2 and 9are reflected on a reflection member having the same configuration,there is a difference of the reflection ratio between the lights fromthe light source 2 and the light source 9, which leads to a possibilityof causing disadvantages such as an increase of scattering due to thedifference.

Therefore in this embodiment, it is preferable to use materials of areflection film or an extinction film on a top 153 c of the raisedportion different from those of the top 151 c. In other words, areflection film (an extinction film) is formed on the top 151 c with amaterial having a great reflectance (an extinction modulus) to awavelength of the light emitted from the light source 2, and areflection film (an extinction film) is formed on the top 153 c with amaterial having a great reflectance (an extinction modulus) to awavelength of the light emitted from the light source 9.

With this configuration, preferably the backward emitting lights fromboth light sources 2 and 9 can be reflected favorably in givendirections (can be favorably absorbed), and therefore the lights arereflected and scattered inside respective packages so as to prevent thelights from being incident on the optical members and light receivingmeans as stray lights.

In this embodiment, the light sources 2 and 9 are different in size fromeach other. An explanation will be made for this point below.

In many cases, an optical output of the light source 2 is different fromthat of the light source 9. This is mainly because their record mediafor recording or reproduction are not identical and therefore therequired quantities of lights are often different from each other.Accordingly, the light source 2 has a heat emitting amount differentfrom that of the light source 9, and therefore there is a differencebetween their temperatures during the operation.

There are the following disadvantages which may be caused when there isa difference between the temperatures of the light sources during theoperation:

A shift of an oscillation wavelength caused by a change of a temperatureand a degradation of optical characteristics accompanying it, and

A degradation or destruction of the light sources caused by a hightemperature, i.e., a reduction of the lives of the light sources. Thesedisadvantages reduce the life of the product and lower its reliability.

In this embodiment, so as to prevent an occurrence of thesedisadvantages, the light source 2 has a size, specifically, an area inwhich the light source 2 is in contact with another member, which isdifferent from that of the light source 9. Since the heat generated bythe light sources is discharged to respective members in contact withthe light sources through conduction, for example, if an output of thelight source 2 is greater than that of the light source 9, a contactarea of the light source 2 larger than that of the light source 9 makesit possible to discharge more heat per unit time from the light source 2through conduction. It is effective to prevent the light source 2 fromhaving a temperature during operation greatly different from thetemperature of the light source 9 during operation, and therefore itprevents an occurrence of the above disadvantages, which leads to longerlife of the product and improved reliability so as to be preferable.

In addition, it is also effective to apply different surface areas tothe light sources 2 and 9. Generally as a form of a heat transmission,there is a radiation (emission) in addition to the conduction describedabove. Since the amount of radiation heat per unit time or unit areadepends on a temperature, a larger surface area generates a greateramount of radiation heat at the same temperature.

Accordingly, if the output of the light source 2 is greater than that ofthe light source 9, a surface area of the light source 2 larger thanthat of the light source 9 generates a greater amount of radiation heatfrom the light source 2 in comparison with the amount of radiation heatfrom the light source 9, so as to reduce the difference of thetemperature between the light source 2 and the light source 9 duringoperation. Accordingly, this configuration is preferable since it iseffective to prevent an occurrence of the above disadvantages, tolengthen the life of the product, and further to improve itsreliability.

As set forth hereinabove, with light sources different in size from eachother according to respective outputs of the light sources in an opticalpickup including a plurality of light sources, different amounts of heatcan be radiated from respective light sources, and therefore it becomespossible to minimize a difference of the temperature between the lightsources during operation, which leads to prevent disadvantages such as ashift of oscillation wavelengths caused by a temperature change of thelight sources, a degradation of the optical characteristics accompanyingit, and a degradation or destruction of the light sources caused by ahigh temperature, in other words, a reduction of preduct lives of thelight sources. Therefore, it is effective to lengthen the life of theproduct in which this type of an optical pickup is installed and toimprove the reliability of the product.

Next, it is preferable to enclose the inside space surrounded by thefirst package 1, in other words, the space in which the light source 2and the light receiving elements 3 are arranged. With thisconfiguration, it becomes possible to prevent dust or moisture frombeing included into the inside of the package, whereby the performancesof the light source 2 and the light receiving elements 3 can bemaintained and it also prevents a degradation of the opticalcharacteristics of the emitted light.

In this embodiment, the first package 1 is closed by the first opticalmember 5. In other words, the bottom of the first optical member 5 isbonded with an outer surface of the sidewall section 1 b of the firstpackage 1 so as to close the opening 1 d provided for the first package1. The bonding materials used here are mostly, for example, opticalhardening resin, epoxy resin, or bonding resign.

It is more preferable to previously enclose N2 gas or inactive gas suchas a dry air or Ar gas in the closed space since it prevents adeterioration of optical characteristics caused by sweating on thebottom of the first optical member 5 which faces the inside of the firstpackage 1 and a degradation of the characteristics caused by oxidationof the light source 2 or the light receiving elements 3.

With this configuration in which the first optical member 5 is bonded tothe sidewall portion 1 b of the first package 1 by using bondingmaterial so as to close the first package 1, a cover glass can beomitted here though it is conventionally needed only for closing thisportion, and therefore a configuration of the optical pickup can besimplified so as to reduce the number of the components. In addition,manufacturing process groups of the optical pickup can be reduced toonly a single process group of positioning and bonding optical membersthough conventionally the manufacturing requires two process groups, thepositioning and bonding optical members and bonding cover member forclosing the package, and therefore the manufacturing processes of theoptical pickup can be simplified so as to improve productivity of theoptical pickup.

Additionally, since the first optical member 5 is exposed to the outsideof the first package 1, the package can be smaller in comparison with aconfiguration in which the first optical member is contained in thepackage, whereby the size of the optical pickup can be also reduced soas to increase an efficiency of utilizing the space of the opticalpickup.

Furthermore, with a configuration in which optical elements are notarranged on the surface which is exposed to the outside but placedbetween prisms in the first optical member 5, it is possible to preventan occurrence of disadvantages, for example, that given performancescannot be maintained since the optical elements are exposed to thesurrounding air and absorbs moisture or that the characteristics aredegraded due to dust on the optical elements.

At this point, an inside pressure of the first package 1 is preferablynegative. It is effective to make the bonding effects favorable betweenthe first optical member 5 and the first package 1 since a pressure isapplied in such a direction that the first optical member 5 bonded tothe sidewall portion 1 b of the first package 1 is drawn from theoutside of the first package 1 to the inside thereof.

Next, there is described below an embodiment having a further preferableconfiguration.

In a configuration of this embodiment, the first package 1 is not closedonly by the first optical member 5 from the outside, but the opening 1 dof the first package 1 is closed by a shield member 85 (indicated by adotted line in the drawing) and the first optical member 5. In otherwords, the shield member 85 is arranged so as to close the opening 1 don the sidewall portion 1 b of the first package 1 from the inside ofthe first package, and the first optical member 5 is arranged so as toclose the opening 1 d on the sidewall portion 1 b of the first packagefrom the outside thereof, and therefore the inside of the first package1 is enclosed by these two members.

Now the advantages of this configuration will be described below. If theinside pressure of the first package 1 is positive, the shield member 85bonded from the inside is pressed to the sidewall portion 1 b includingthe bonding material, which is effective to decrease a possibility of anoccurrence of a leak. If it is negative, however, the pressure isapplied in such a direction that the shield member 85 is separate fromthe sidewall portion 1 b, which increases the possibility of anoccurrence of a leak due to defective bonding.

To the contrary, the first optical member 5 bonded from the outside ispressed to the sidewall portion 1 b including the bonding material ifthe inside pressure of the first package 1 is negative as opposite tothe shield member 85, which is effective to decrease the possibility ofan occurrence of a leak, but if the inside pressure of the first package1 is positive, the pressure is applied in such a direction that thefirst optical member 5 is separated from the sidewall portion 1 b, whichincreases the possibility of an occurrence of a leak due to defectivebonding.

In other words, with the shield member 85 and the first optical member 5arranged so that the sidewall portion 1 b of the first package 1 is putbetween them, a pressure is applied in such a direction that at leastone of the shield member 85 and the first optical member 5 is pressed tothe sidewall portion 1 b whether the inside pressure of the firstpackage 1 is positive or negative, and therefore it becomes possible toreduce occurrences of a leak caused by a difference of atmosphericpressure or defective bonding.

With this configuration, the air-tightness of the inside of the firstpackage 1 can be improved, whereby it becomes possible to prevent anoccurrence of disadvantages caused by a condition that the light source,the light receiving element, or the optical member to be arranged insidethe first package 1 is exposed to the air or includes moisture, whichleads to achieving an optical pickup with an extremely high reliability.

For the material of the shield member 85, it is preferable to use amaterial having favorable transparency such as resin or glass which doesnot decrease an efficiency of utilizing light. In addition, a thinnershield member is preferable to an extent that it does not cause anysignificant problem since it is effective to minimize an expansion of adiameter of the light.

Furthermore, the bonding power of the shield member 85 to the sidewallportion 1 b is preferably different from that of the first opticalmember 5 to the sidewall portion 1 b. Particularly, with the bondingpower of the shield member 85 directly facing the inside of the firstpackage 1 to the sidewall portion 1 b being greater than that of thefirst optical member 5, a leak between the first optical member 5 andthe sidewall portion 1 b can be inhibited to extend to the inside of thefirst package 1 even if such a leak may occur. This is effective tolargely decrease a possibility of an occurrence of a leak into theinside of the first package 1. As a means for realizing thisconfiguration, there can be provided a method of using a bondingmaterial having a greater bonding power for the bonding between theshield member 85 and the sidewall portion 1 b in comparison with that ofthe bonding material used for the bonding between the first opticalmember 5 and the sidewall portion 1 b.

Still further, preferably a difference of pressure is as small aspossible between a space A enclosed by the first package 1 and theshield material 85 and a space B enclosed by the sidewall portion 1 b,the shield member 85, and the first optical member 5. A pressure isalways applied to the shield member 85 between the space A and the spaceB due to a difference of pressure between the space A and the space B.If a vibration caused by hand carriage or car mounting of the product isentered into the shield member 85 in this condition, the shield member85 significantly vibrates or is deflected and this may change minutelyan angle of incidence formed by an incident light and the shield member85, and may further lead to a degradation of optical characteristics.From this viewpoint, the difference of the pressure (P) is preferably assmall as possible between the space A and the space B. Specifically, Pis preferably 0.3 (atm) or lower.

The same conditions are preferably applied to the spaces surrounded bythe second package 8 and the second optical member 11.

Next, the optical path dividing means 15 is used to guide light emittedfrom both of the light source 2 and the light source 9 to the opticaldisk. Generally a half mirror or a polarizing separation (polarizationbeam splitter)film is used as a material of the optical path dividingmeans 15, and more preferably it has characteristics of transmitting thelight from the light source 2 at a high ratio and of reflecting thelight from the light source 9 at a high ratio. If so, a loss of thelight in the optical path dividing means 15 can be limited to theminimum and therefore an efficiency of utilizing the light can beincreased. The increase of the efficiency of utilizing the light ispreferable since it makes it possible to limit an amount of lightemitted from the light source 2 or the light source 9, whereby the lifeof the light source 2 or the light source 9 can be lengthened, whichleads to an improvement of the reliability of an optical disk unit onwhich this optical pickup is mounted.

Preferably a reflection means having a wavelength selecting function isused as the optical path dividing means 15 having the abovecharacteristics. The reflection means having this wavelength selectingfunction transmits light having a certain wavelength while it reflectslight having another wavelength, and particularly in this embodiment,with the optical path dividing means 15 configured so as to transmitalmost all the light from the light source 2 and to reflect almost allthe light from the light source 9, the efficiency of utilizing the lightfrom the light source 2 and the light source 9 can be set to thehighest. Accordingly, a great load is not applied almost at all toeither the light source 2 or the light source 9, and therefore the livesof the light source 2 and the light source 9 can be averaged and itfavorably leads to actualizing a long life of the optical pickup.

Next, a color (chromatic) aberration correcting (compensating) means500, which is placed between the light source 9 and the optical pathdividing means 15, is used to correct a color (chromatic) aberrationwhich may occur in a luminous flux which is emitted from the lightsource 9 and converges on a disk 19. As the above color (chromatic)aberration correcting (compensating) means 500, there may be a hologramhaving a color (chromatic) aberration correcting (compensating) means ora lens having a color (chromatic) aberration correcting (compensating)means; it is preferable to use the hologram to actualize a smalleroptical pickup. This is because it is effective to lower a ratio of avolume of the color (chromatic) aberration correcting (compensating)means to the optical pickup and it further decreases the size of theoptical pickup.

With this color (chromatic) aberration correcting (compensating) means500 arranged, it is possible to correct an occurrence of a color(chromatic) aberration caused by a change of a refractive index of aglass material or the like due to a difference between a wavelength ofthe light emitted from the light source 2 and that of the light emittedfrom the light source 9, and therefore it becomes possible to resolve aproblem that the light condensed by the condenser is not condensed onthe record medium due to a presence of a color (chromatic) aberration.In other words, it is unnecessary to use an objective lens which isoptimally-designed according to a type of the disk and a wavelength ofthe light source. Accordingly, without a configuration in which anobjective lens is exchanged according to a type of the disk and that ofthe light source, only a single condenser 17 can be used to favorablycondense both of the light from the light source 2 and the light fromthe light source 9 on a high-density optical disk 18 and a low-densityoptical disk 19, respectively.

Although the color (chromatic) aberration correcting (compensating)means 500 is arranged between the light source 9 and the optical pathdividing means 15 in this embodiment, it may be placed between theoptical path dividing means 15 and the condenser 17 as a configurationin which it does not so much affect the characteristics of the lightfrom the light source 2 with an amount of application to the light fromthe light source 2 made smaller than an amount of application to thelight from the light source 9. With this configuration in which thecolor (chromatic) aberration correcting (compensating) means 500 can beplaced in any position between the light source 9 and the condenser 17,a degree of freedom in designing an optical pickup can be increased soas to actualize a smaller optical pickup easily.

Although the quarter-wavelength plate 4 and the quarter-wavelength plate14 are mounted on the first optical member 5 and the second opticalmember 11, respectively, in this embodiment, they may be placed in anyposition between an end surface of the optical path dividing means 15 inthe side of a collimator lens 16 and the optical disk, instead. Withthis configuration, one quarter-wavelength plate can be omitted thoughconventionally two quarter-wavelength plates are needed, and thereforethe productivity can be enhanced and a low-cost optical pickup can beachieved. Particularly, the plate is preferably formed on the endsurface of the optical path dividing means 15 in the side of thecollimator lens 16 previously in the configuration since it reduces thenumber of processes so as to improve the productivity.

The collimator lens 16 is used to convert diffusion angles of the lightemitted from the light source 2 and the light source 9 to parallel lightwhich has been diffused light before it is incident.

The condenser 17, which is used to condense the light which has beenincident and then to form a beam spot on the optical disk, is supportedby a lens driving means so as to shift in a focusing or trackingdirection. The collimator lens 16 is effective to increase a quantity oflight which is incident on the condenser 17, and therefore an efficiencyof utilizing the light is increased. Accordingly, it becomes possible touse the light source 9 at an output significantly lower than the maximumoutput, so as to lengthen the life of the light source 9, whereby thereliability of the optical pickup device is increased.

In this embodiment, the collimator lens 16 and the condenser 17 aredesigned so as to be optimum for the light source 2 and the high-densityoptical disk 18, and the luminous point 2 a of the light source 2 isarranged on a focus of the collimator lens 16.

Furthermore, although the color (chromatic) aberration correcting(compensating) means 500 is provided with being separated from the lightsource package 8 and the optical path dividing means 15 in thisembodiment, it may be formed on the light source package 8 after anadjustment of an optical axis with the light source 9 or may bemonolithically integrated with the optical path dividing means 15 ordirectly formed on its end surface in the side of the light sourcepackage 8. It simplifies an assembly process of the optical pickup, soas to increase the productivity of the optical pickup.

Still further, instead of using the collimator lens 16, for example, thefirst optical member 5 and the second optical member 11 may be providedwith a function of converting diffusion angles of the light. In thisconfiguration, the collimator lens 16 need not be provided, andtherefore precise positioning becomes unnecessary and the number of thecomponents is reduced, whereby the productivity is increased.

Next, an operation of the optical pickup device having theseconfigurations will be described with reference to the drawings.

First, the high-density optical disk 18 is installed in a spindle motorof the disk unit. Mostly the high-density optical disk 18 is made of twodisk substrates each having a thickness of approximately 0.6 mm withbeing laminated to be formed. In this condition, the optical pickup isoperated.

The luminous flux 2 b emitted from the luminous point 2 a of the lightsource 2 is transmitted through the optical path dividing means 6 on thefirst inclined plane 5 a of the first optical member 5, changes itspolarization direction from a linear polarization to a circularpolarization at the quarter-wavelength plate 4, and is incident on theoptical path dividing means 15. Then, after it is transmitted throughthe optical path dividing means 15 almost entirely, it is converted to aluminous flux 2 c at the collimator lens 16 and condensed as shown by aluminous flux 2 d. The condenser 17 is designed with a numericalaperture of approximately 0.6 so that it can focus light into a minutespot to an extent that data on the high-density optical disk 18 can bereproduced.

Next, by using FIG. 1, an explanation will be made for an optical pathof forward light for a reproduction of the low-density optical disk 19.In this embodiment, the low-density optical disk 19 has a thickness ofapproximately 1.2 mm. Light 9 b emitted from a luminous point 9 a of thelight source 9 is transmitted through the optical path dividing means 12on the first inclined plane 11 a of the second optical member 11,changes its polarization direction from a linear polarization to acircular polarization at the quarter-wavelength plate 14, and isincident on the optical path dividing means 15. Then, after it isreflected by the optical path dividing means 15 almost entirely, it isconverted to a luminous flux 9 c at the collimator lens 16, and thencondensed as shown by a luminous flux 9 d on the low-density opticaldisk 19 by the condenser 17.

At this point, a focal length L2 of the condenser 17 for a reproductionof the low-density optical disk 19 is set to a length longer than afocal length L1 of the condenser 17 for a reproduction of thehigh-density optical disk 18. A difference between the focal lengths ispreferably 1.0 mm or lower, otherwise, 0.6 mm or lower since it makes italmost unnecessary to drive greatly an actuator which holds thecondenser 17 at a reproduction on various types of a plurality of disks.Accordingly, the position of the focus can be easily adjusted andtherefore it is possible to cope with a difference of a thicknessbetween the substrates very favorably.

With this configuration in which light from a plurality of light sourcesfocuses in different positions on the record media, it becomes possibleto reproduce data on record media whose substrate thickness is differentfrom each other by means of an identical optical pickup device. In otherwords, it becomes possible to record and reproduce data on thelow-density optical disk 19 having a thickness of 1.2 mm such as aCD-ROM and data on the high-density optical disk 18 which is a singlesubstrate having a thickness of 0.6 mm or a DVD with the double-sidedlamination of the single substrate by means of an identical opticalpickup device.

The focal length L1 and the focal length L2 can be changed to someextent by setting a movable range of the optical member such as thecondenser 17, and therefore it is possible to reproduce data on anoptical disk made of laminated high-density optical disks or on anoptical disk having a plurality of record layers.

Next, an explanation will be made for an optical path up to the point atwhich reflected light from the high-density optical disk 18 or thelow-density optical disk 19 is detected, in other words, a backwardpath.

First, a reproduction on the high-density optical disk 18 is described.Reflected light from the high-density optical disk 18 is transmittedthrough the optical path dividing means 15 along almost the same opticalpath as the forward path, converted by the quarter-wavelength plate 4from the circular polarization to the linear polarization which crossesat right angles to the first polarization direction, and then incidenton the optical path dividing means 6 on the first inclined plane 5 a ofthe first optical member 5. Since the optical path dividing means 6 ismade of a polarizing separation (polarization beam splitter) film inthis embodiment, the incident light is reflected almost entirely andthen guided to the reflection means 7. The reflection means 7 iscomposed of optical elements satisfying a certain object; there areprovided elements for forming focus error signals here. Accordingly, thelight reflected by the reflection means 7 is condensed on the lightreceiving means 3 while forming a focus error signal to detect a signaldepending on the data recorded on the high-density optical disk 18, atrack error signal, and a focus error signal.

Next, a reproduction on the low-density optical disk 19 will bedescribed. Reflected light from the low-density optical disk 19 isreflected by the optical path dividing means 15 along almost the sameoptical path as the forward path, converted by the quarter-wavelengthplate 14 from the circular polarization to the linear polarization whichcrosses at right angles to the first polarization direction, and thenincident on the optical path dividing means 12 on the first inclinedplane 11 a of the second optical member 11. Since the optical pathdividing means 12 is made of a polarizing separation (polarization beamsplitter) film in this embodiment, the incident light is reflectedalmost entirely and then guided to the reflection means 13. Thereflection means 13 is composed of optical elements satisfying a certainobject; there are provided elements for forming focus error signalshere. Accordingly, the light reflected by the reflection means 13 iscondensed on the light receiving means 10 while forming a focus errorsignal to detect a signal depending on the data recorded on thelow-density optical disk 19, a track error signal, and a focus errorsignal.

If a plurality of light sources are arranged in different positions asdescribed above, mostly there is a great difference in a wavefrontaberration which occurs in the light emitted from respective lightsources and therefore it is necessary to use a lens having an aberrationcorrecting (compensating) function effective for correcting(compensating) this wavefront aberration as a condenser, which oftenresults in causing a necessity of using a plurality of condensersmatching each luminous flux in general. In this embodiment, this problemis avoided by optimizing a distance between the luminous point 2 a or 9a of the light source 2 or 9 and the collimator lens, and this pointwill be now described below.

Referring to FIG. 4, there is shown a relationship between the luminouspoint and the collimator lens in the first embodiment. In FIG. 4,reference numeral L3 indicates an effective focal length from thecollimator lens 16 to the luminous point 2 a, and reference numeral L4indicates an effective focal length from the collimator lens 16 to theluminous point 9 a. Furthermore, referring to FIG. 5, there is shown arelationship between a wavefront aberration amount and a distance ratiodepending on a shift amount of the condenser of the first embodimentaccording to the present invention. In other words, when a ratio of L3to L4 is changed, a wavefront aberration amount which occurs at anincidence on the condenser is compared between a case in which thecondenser 17 shifts by 500 μm in a tracking direction (indicated by athick line) and a case in which it does not shift in the trackingdirection at all (indicated by a thin line).

In general, a condenser under reproduction on an optical disk has apossibility of shifting by a maximum of 500 μm in a tracking direction.In addition, taking into consideration that it is assumed that 0.07λ(where λ indicates a wavelength of light) or lower of a wavefrontaberration amount as an RMS value is allowed to converge light which hasbeen incident on the condenser into the optical disk effectively, andassuming that the wavefront aberration amount is 0.07λ or lower at themaximum shift amount (500 μm) of the condenser 17 for the light from theluminous point 9 a in which the aberration amount is relatively largeand the incidence conditions to the condenser 17 become severe, lightfrom both of the luminous points will converge on the optical diskindependent of the shift amount of the condenser 17 after it is incidenton the condenser 17. To satisfy this condition, apparently as shown inFIG. 5, the ratio of L3 to L4 (L4÷L3=H, it is described hereinafter asH) is preferably within a range of 0.50≦H≦0.75.

If H is within this range, it is possible to limit the amount of awavefront aberration which may occur in the light reflected by therecord medium and return, and therefore the light can be favorablyincident on the light receiving means which receives the reflectionlight so as to achieve superior signal characteristics.

Further, if the wavefront aberration amount is 0.04λ or lower as an RMSvalue under the same conditions, the light incident on the condenser 17is converged very precisely on the optical disk independently of a shiftamount of the condenser 17 whether the incident light is emitted fromeither luminous point 2 a or 9 a. To satisfy this condition, apparentlyas shown in FIG. 5, the ratio of L3 to L4 (H) is preferably within arange of 0.53≦H≦0.70.

With an arrangement of the optical system so that the value of H iswithin the above range, the wavefront aberrations in every luminous fluxcan be theoretical threshold or lower values in an optical pickup havinga plurality of types of luminous flux in a single optical system, andtherefore every luminous flux can be condensed on the optical disk byusing a single condenser 17.

Accordingly, only one condenser 17 is needed for condensing, so that thenumber of condensers can be reduced. In addition, if a plurality ofcondensers are used, it is not required to arrange a plurality ofoptical systems corresponding to them nor lens switching means, wherebyit becomes possible to make the optical pickup smaller, to increase theproductivity due to a decrease of the number of the components, andfurther to improve the reliability of the optical pickup and to increasethe operation speed due to omission of a complicated mechanism.

Although an infinite optical system having the collimator lens 16 isused in this embodiment, a finite optical system without the collimatorlens as shown in FIG. 6 may be also used. Referring to FIG. 6, there isshown a relationship between luminous points and a condenser in thefinite optical system in the first embodiment according to the presentinvention. In FIG. 6, the configuration is the same as for the infiniteoptical system except that reference numeral L5 indicates an effectivefocal length from the condenser 17 to the luminous point 2 a, andreference numeral L6 indicates an effective focal length from thecondenser 17 to the luminous point 9 a. Still further, also in anoptical pickup in which one is an infinite optical system and the otheris a finite optical system, the relationship can be defined in the samemanner.

The above phenomenon may be caused by an extremely small sphericalsurface aberration as a whole since a degree of a spherical surfaceaberration caused by a difference of a thickness between thehigh-density optical disk and the low-density optical disk is the sameas that of a spherical surface aberration caused by a deviation of theposition of the luminous point 9 a and they have inverse signs whichnegates the spherical surfaces each other.

Furthermore, referring to FIG. 19, there is shown a diagram of arelationship between a lens shift amount and a wavefront aberrationamount depending on a presence or absence of a color (chromatic)aberration correction of the first embodiment according to the presentinvention, illustrating the wavefront aberration amount of luminous fluxemitted from the light source 9 and converging on the disk 19 when thecondenser 17 is shifted in the tracking direction assuming that the Hvalue is 0.63 in a case that the color (chromatic) aberration correcting(compensating) hologram 500 is arranged between the light source 9 andthe collimator lens 16 (indicated by a thick line) and in a case that itis not arranged between them (indicated by a thin line). In general, acondenser under reproduction on an optical disk has a possibility ofshifting by a maximum of 500 μm in a tracking direction. To limit thewavefront aberration amount within the above tolerance in this range ofthe lens shift amount, as apparently shown in FIG. 19, it is required toinstall the color (chromatic) aberration correcting (compensating)hologram 500. The color (chromatic) aberration correcting (compensating)hologram 500 is preferably installed between the light source 9 and theoptical path dividing means 15 so as not to affect the luminous fluxwhich is emitted from the light source 2 and converges on the disk 18.

Unless the color (chromatic) aberration correcting (compensating)hologram 500 is installed, a wavefront aberration at a lens shiftbecomes relatively great. This is because the collimator lens 16 and thecondenser 17 are designed so as to be optimum to the wavelength of thelight emitted from the light source 2, and therefore a color (chromatic)aberration is generated to the luminous flux emitted from the lightsource 9 having a different wavelength. A color (chromatic) aberrationis caused by a change of a refractive index of a glass material or thelike composing the lens caused by a wavelength, which causes a change ofa refraction power of the lens and a deviation of a focus position ofthe luminous flux transmitted through a central portion of a lens fromthat of the luminous flux transmitted though a peripheral portion of thelens.

Accordingly, the color (chromatic) aberration correcting (compensating)means 500 in this embodiment corrects the deviation of the focusposition of the luminous flux transmitted through the central portion ofthe collimator lens or the condenser from that of the luminous fluxtransmitted through the peripheral portion of the lens, so that all thelight rays transmitted through the lens converge on almost a singlefocus position.

In this embodiment, a correction is made for a spherical surfaceaberration caused by a difference of a thickness between the disks withoptimizing a distance between the luminous point 9 a of the light source9 and the collimator lens 16, and a correction is made for a color(chromatic) aberration caused by a difference of a wavelength betweenthe light sources with installing the color (chromatic) aberrationcorrecting (compensating) means between the luminous point 9 a of thelight source 9 and the collimator lens 16, so that the wavefrontaberrations in every luminous flux can be tolerances or lower in anoptical pickup having a plurality of types of luminous flux in a singleoptical system, and therefore every luminous flux can be condensed onthe optical disk by using a single condenser 17.

[Second Embodiment]

A second embodiment of the present invention will be described belowwith reference to the accompanying drawings.

Referring to FIG. 7, there is shown a cross section of an integratedoptical head of a second embodiment according to the present invention.

In FIG. 7, a package 20 comprises a light source 2 for emitting lightfor a high-density optical disk 18 and a light source 9 for emittinglight for a low-density optical disk 19, a substrate portion 20 a onwhich a light receiving means 21 or the like are mounted to receivelight reflected by a record medium, and a sidewall portion 20 b arrangedso as to enclose these members. The substrate portion 20 a and thesidewall portion 20 b and others can be formed either integrally orseparately. If they are integrally formed, an assembly process can besimplified so as to increase the productivity.

Materials of the package 20 are almost the same as for the first package1 of the first embodiment, and therefore their explanation is omittedhere.

The package 20 discharges a heat generated by the light sources 2 and 9to the outside by making the substrate portion 20 a and, if necessary,the sidewall portion 20 b in contact with a carriage having a greatthermal capacity. Accordingly, as an area of the substrate portion 20 ain contact with the carriage becomes larger, the package 20 obtains morefavorable heat dissipation effects.

Still further, in the substrate portion 20 a, there are providedterminals 20 c for supplying power to the light sources 2 and 9 and fortransmitting electric signals from the light receiving means 21 to anarithmetic circuit. These terminals 20 c have almost the sameconfiguration as for the terminals 1 c described in the firstembodiment, and therefore the explanation is omitted here.

There can be various combinations of the light source 2 and the lightsource 9 contained in the package 20, for example, 650 nm and 780 nm,490 nm and 650 nm, or 400 nm and 650 nm. In other words, preferably awavelength of one light source is longer and that of the other lightsource is shorter than it. The number of installed light sources can beeither two or three.

In an opening 20 d of the package 20, an optical member 22 is bonded bya bonding medium such as bonding glass or bonding resin.

As shown in the drawing, it is preferable to enclose the inside spacesurrounded by the package 20 and the optical member 22, in other words,the space in which the light sources 2 and 9 and the light receivingmeans 21 are arranged. With this configuration, it becomes possible toprevent impurity such as dust or moisture from being included into theinside of the package, whereby the performances of the light sources 2and 9 and the light receiving means 21 can be maintained and it alsoprevents a degradation of the optical characteristics of the emittedlight. Further, it is more preferable to previously enclose N2 gas orinactive gas such as a dry air or Ar gas in the space enclosed by thepackage 20 and the optical member 22 since it prevents a deteriorationof optical characteristics caused by sweating on the surface of theoptical member 22 or the like facing the inside of the package 20 and adegradation of the characteristics caused by oxidation of the lightsources 2 and 9 or the light receiving means 21.

In addition, in comparison with a case in which the light source 2 iscontained in a different package from that of the light source 9, theycan have the same environment inside the package, so as to achieve thesame operating conditions for the light source 2 and the light source 9.Accordingly, it is effective to prevent an occurrence of disadvantagessuch as a difference of a life between the light source 2 and the lightsource 9 caused by a difference of the operating conditions betweenthem, whereby the reliability of the optical pickup can be enhanced.

The optical member 22 is used to guide the light emitted from the lightsource 2 and the light source 9 to a given optical path and to guide thereturning light reflected by the high-density optical disk 18 or thelow-density optical disk to the light receiving means 21.

The optical member 22 comprises a first substrate 22 d including a firstinclined plane 22 a, a second inclined plane 22 b, and a third inclinedplane 22 c and a second substrate 22 e bonded to an end surface of thefirst substrate 22 d in the side of the light source.

The optical member 22 is preferably formed in a shape of a parallelplanar plate as a whole since it is effective to prevent an occurrenceof aberration, whereby favorable reproduction signals or focus trackingsignals can be formed. Furthermore, preferably the optical member 22 ismounted so that its top and bottom are precisely perpendicular to theoptical axis of the transmitted light since it is effective to preventan occurrence of the non-point aberration (astigmatism) and adegradation of reproduction signals caused by an unfocused spot.

As for materials of the optical member 22, it is preferable to usematerials having a high light transmission such as glass or resin sinceit is effective to prevent a decrease of the quantity of light and adegradation of the optical characteristics of the light transmittedthrough the optical member 22. Particularly, glass is preferable as amaterial of the optical member 22 since it does not cause abirefringence and therefore the characteristics of the transmitted lightcan be favorably maintained. Furthermore, it is more preferable to useoptical glass having a low wavelength dispersion, in other words, a highAbbe's number such as a BK-7 since it is effective to prevent anoccurrence of an aberration of a spherical surface caused by afluctuation of a wavelength.

At this point, the optical member 22 has a configuration in which thereare respective normal vectors at almost the same angle of inclination asfor the first inclined plane 22 a, the second inclined plane 22 b, andthe third inclined plane 22 c in almost the same direction. With thefirst inclined plane 22 a, the second inclined plane 22 b, and the thirdinclined plane 22 c formed in this manner, a predetermined opticallength can be achieved while decreasing the length of the firstsubstrate 22 d and therefore that of the optical member 22 in its heightdirection, whereby the size of the optical pickup can be reduced whilethe given optical characteristics are maintained. Particularly, thecenter of gravity of the optical head is placed in a position near anarea in which the package 20 is installed when the package 20 comprisingthe optical member 22 is installed into a carriage, and therefore a highaccuracy of installation can be achieved and a deviation of a positionat bonding can be prevented at a high percentage.

In addition, various optical elements can be arranged in the positionswhere light is reflected on respective planes, and thereforepredetermined optical characteristics can be given to the light incidenton the optical member 22 when it is transmitted.

Particularly when the light from a plurality of light sources is guidedto an identical optical path as described in this embodiment, preferablyat least three planes are formed with being inclined in the samedirection in the optical member 22, so that the light from at least onelight source is reflected twice or more, whereby it becomes possible tooptimize the optical characteristics of the light emitted from the lightsource 2 or the light source 9 before the light is transmitted from theoptical member 22 by passing the light through various optical membersformed on respective inclined planes.

With this configuration, a long distance can be secured from the lightsource 2 or the light source 9 to an emission surface of the opticalmember 22 and therefore to the contrary a distance between the opticalmember 22 and the record medium can be decreased, so that the size ofthe optical pickup can be reduced. In addition, it becomes possible togive optical characteristics required for irradiating the record mediumin the optical member 22, and therefore it is unnecessary to arrangespecially various optical members in the optical path of the light whichhas been emitted from the optical member 22, whereby the number of thecomponents or an assembly cost can be reduced.

Additionally, with the first inclined plane 22 a, the second inclinedplane 22 b, and the third inclined plane 22 c having the same angle ofinclination, the optical member 22 can be easily manufactured at a highprecision by bonding a plurality of parallel plane plates with beingcombined on which given optical elements are previously formed andcutting off at a given angle, and therefore the productivity of theoptical member 22 is significantly increased. Furthermore, due to thepredetermined angle, an optical axis can be easily adjusted so as toreduce the time and processes required for axis adjustment.

The angle of inclination on the first inclined plane 22 a, the secondinclined plane 22 b, and the third inclined plane 22 c to incident lightis preferably within the range of 30 deg to 60 deg, further preferablyapproximately 45 deg. The first inclined plane 22 a, the second inclinedplane 22 b, and the third inclined plane 22 c are preferably spacedapart from each other by a given distance from a viewpoint of theoptical elements formed on respective inclined planes. Unless theoptical elements are spaced apart from each other by a given distance,it increases a possibility of causing a disadvantage that a smallquantity of light transmitted without being reflected comes into theoptical path of emitted luminous flux and becomes a component of a straylight.

Assuming that L is the given distance, if the angle of inclination ofthe inclined planes is smaller than 30 deg, the optical member 22 ismade thicker at least by a difference of the incident light position2L/{square root over ( )}(3) which is generated until the light isreflected on the first inclined plane 22 a and is incident on the secondinclined plane 22 b or until it is reflected on the second inclinedplane 22 b and is incident on the third inclined plane 22 c, and furtherif the angle is greater than 30 deg, a difference of an incident lightposition generated for securing the same distance L, and therefore, avolume of the first optical member 5 is increased by that amount, whichmakes it hard to reduce the size of the optical pickup.

If the angle of inclination of the inclined planes is greater than 60deg, the volume of the optical member 22 is increased as describedabove, too. Therefore, downsizing of the optical pickup becomes harder.

Particularly if the angle of inclination is approximately 45 deg, it ispossible to decrease a difference of the incident light position almostto zero in the light which is reflected on the first inclined plane 22 aand is incident on the second inclined plane 22 b and the light which isreflected on the second inclined plane 22 b and is incident on the thirdinclined plane 22 c, whereby the optical member 22 can be downsized mostefficiently, and therefore favorably the size of the optical pickup canbe efficiently reduced, too.

Next, various optical elements in the optical member 22 will beexplained.

A diffusion angle converting (light beam diameter changing rate alongbeam axis adjusting) means 23, which is arranged so as to match theoptical axis of the light emitted from the light source 2 on an endsurface 22 f of the second substrate 22 e in the side of the lightsource, is used to decrease a diffusion (light beam diameter changing)angle of the light incident from the light source 2, in other words, toconvert the optical path of the light emitted from the luminous point 2a of the light source 2 as if it were emitted from a position fartherthan a visual position, and it shifts the luminous point in a virtuallyopposite direction from the record medium so as to elongate the opticalpath from the light source to the record medium. The diffusion angleconverting means 23 is preferably made of a diffraction grating,particularly a hologram since it can transmit light very efficiently.Particularly as a hologram, it is preferable to use one having a crosssection in a shape of a staircase of four or more steps or having aserrated cross section, since the light can be used very efficiently andthe quantity of light can be prevented from being decreased.

A filter 24, which has a wavelength selectivity, transmits the lightguided from the light source 2 almost completely and reflects the lightguided from the light source 9.

With the filter 24 formed on the first inclined plane 22 a, the lightguided from the light source 9 can be reflected without interrupting thelight emitted from the light source 2 almost at all, and therefore thelight emitted from the light source 2 and the light source 9 can beguided to the record medium at a high percentage. Accordingly, data canbe recorded into or reproduced from the record medium without increasingthe quantity of light emitted from the light source 2 and the lightsource 9, and therefore it is possible to prevent the lives of the lightsource 2 and the light source 9 from being reduced by an operation ofthe light source 2 or the light source 9 at a high power output.Furthermore, since the light source 2 and the light source 9 can be usedat a low power output, an increase of a temperature of the light source2 and the light source 9 can be restrained, and therefore theoscillation wavelength cannot easily shift at a temperature change.Accordingly, it is possible to provide a high-performance optical pickupwhich is capable of forming a focus more precisely.

In this embodiment, the filter 24 is also used as a diaphragm for thelight from the light source 9. Although the light from both of the lightsource 2 and the light source 9 is allowed to be incident on a singlecondenser 17, an incident pupil of the condenser 17 is adjusted so as tofocus on a record area of the high-density optical disk 18. Accordingly,in this embodiment, the shape and the material of the condenser 17 areadjusted so that the light from the light source 2 is condensed on therecord area of the high-density optical disk 18.

To cause the light from the light source 9 to focus on a record area ofthe low-density optical disk 19 with this condenser 17, in thisembodiment, the condenser is adjusted so that a diameter of the lightemitted from the light source 9 and incident on the condenser 17 issmaller than that of the light from the light source 2. Generally, alens has a stronger condensing application in a peripheral portion thanin a central portion. Therefore, if expanded light is incident, thefocus is formed in a nearer position; if light which is not expanded somuch is incident, the focus is formed in a farther position. In thisembodiment, the record area of the low-density optical disk 19 isarranged in a farther position than that of the high-density opticaldisk 18, and therefore by optimizing an incidence aperture of the lightfrom the light source 9 to the condenser 17, the light from the lightsource 9 can be condensed on the record area of the low-density opticaldisk 19 by using the condenser 17 which is designed with being tailoredto the light from the light source 2.

The incidence aperture is adjusted by the filter 24. In other words, thesize of the filter 24 is adjusted so that the light reflected by thefilter 24 has a given diameter on the condenser 17.

With the filter 24 having this diaphragm function, a diameter of thelight emitted from the light source 9 can be precisely adjusted, andtherefore a diameter of the light incident on the condenser 17 can beset to a given size, whereby the light from the light source 9 can becondensed on the record area of the low-density optical disk 19 by thecondenser 17. Additionally, in comparison with a case in which thediaphragm is arranged separately, the number of the components can bedecreased and further it is possible to omit the time and process foradjusting a distance between the positions of the diaphragm and thelight source 9, and therefore the productivity of the optical pickup canbe increased.

Furthermore, with the diaphragm arranged in this position, light whichis not reflected by the filter 24 though it has been emitted from thelight source 9 is directly transmitted through the first inclined plane22 a and then discharged to the outside of the optical member 22, andtherefore it is possible to prevent the light from becoming stray lightin the package 20 even if it is not reflected.

In addition, the filter 24 is arranged in a position where forward lighttoward the low-density optical disk 19 is incident though backward lightreflected by the low-density optical disk 19 is not incident. With thefilter 24 having the diaphragm function with being arranged in thisposition, for example, even if an optical axis of backward light isdeviated from a predetermined position by a shift of the condenser 17,the light does not pass through the diaphragm and therefore it ispossible to prevent the light originally to be incident on the lightreceiving means from being interrupted, which decreases the quantity oflight incident on the light receiving means, and to prevent anunbalanced distribution of the quantity of light from being generated.Accordingly, more precise RF signals can be favorably obtained andfocusing or tracking servo signals can also be formed more accurately.

Furthermore, the filter 24 has a favorable configuration, since itaffects the light from the light source 9 though it does not affect thelight from the light source 2 and therefore the diaphragm for the lightfrom the light source 9 does not interrupt the light from the lightsource 2 nor does it have a bad influence upon the light from the lightsource 2, whereby, particularly in an optical pickup having aconfiguration in which a plurality of light sources are contained in asingle package and light from a plurality of light sources is condensedin a given position by a single condenser, the light from a plurality oflight sources can be incident at a given diameter on the condenserwithout a bad influence on each light.

A polarizing separation (polarization beam splitter) film 25 transmitslight in a specific polarization direction and reflects light in otherpolarization directions. In this embodiment, the polarizing separationfilm 25 has a configuration so that it transmits S polarizationcomponents emitted from the light sources 2 and 9 and reflects Ppolarization components. With this polarizing separation film 25,transmitted light can be guided to the record medium without thequantity of the transmitted light being decreased almost at all, wherebyfavorably it is possible to improve the efficiency of utilizing light,which leads to achieving longer lives of light sources 2 and 9.

A color (chromatic) aberration correcting (compensating) means 501 hasalmost the same functions as for the color (chromatic) aberrationcorrecting (compensating) means 500 in the first embodiment. In thisembodiment, the color (chromatic) aberration correcting (compensating)means 501 is placed at an end surface of the first substrate 22 d in theopposite side from the light sources so as to match the light axis ofthe light emitted from the light source, particularly having a functionof correcting (compensating) a color (chromatic) aberration which mayoccur in a luminous flux which is emitted from the light source 9 andconverges on a disk 19.

A quarter-wave(length) plate 26 has functions of converting incidentlight from a linear polarization to an elliptic polarization and ofconverting an elliptic polarization reflected by the record medium withits rotating direction being inverted to a linear polarization whichcrosses at right angles to the polarization direction of the aboveincidence.

A diffusion angle converting (light beam diameter changing rate alongbeam axis adjusting) means 27, which is arranged so as to match theoptical axis of the light emitted from the light source 9 on an endsurface 22 f of the second substrate 22 e in the side of the lightsource, is used to make negative a diffusion (light beam diameterchanging) angle of the light incident from the light source 9, in otherwords, to convert the optical path of the light emitted from theluminous point 9 a of the light source 9 as if it were emitted from aposition nearer than a visual position, and it shifts the luminous pointin a virtually approaching direction to the record medium. It apparentlyshifts the luminous point of the light source 9 from the luminous point9 a to the luminous point 9 e, and therefore shortens the optical pathfrom the light source 9 to the record medium. The diffusion angleconverting means 27 is preferably made of a diffraction grating,particularly a hologram since it can transmit light very efficiently.Particularly as a hologram, it is preferable to use one having a crosssection in a shape of a staircase of four or more steps or having aserrated cross section, since the light can be used very efficiently andthe quantity of light can be prevented from being decreased.

A means for forming a plurality of beams 28 is used to reflect incidentlight with separating it to a plurality of types of luminous flux, andin this embodiment, it separates light passing through the diffusionangle converting means 27 into three types of luminous flux and reflectsthem toward the filter 24. The means for forming a plurality of beams 28is preferably formed by a diffraction grating since a plurality of typesof luminous flux can be formed efficiently. In this embodiment, it has aconfiguration in which three types of luminous flux, zero-dimensionallight and plus or minus one-dimensional light, generated in thediffraction grating are mainly formed. An area in a given position of atrack of the low-density optical disk 19 is irradiated with a pluralityof types of luminous flux formed here, and then the quantities ofreturning light are compared with each other, so as to be subjected to atracking method commonly called a three-beam method for tracking on thelow-density optical disk 19. Therefore, unless the three-beam method isnot used as a tracking method, it is preferable to arrange a reflectionmeans simply or an optical device for generating light needed for thetracking method.

Reflection means 29 and 30 are used to reflect light which has beenreflected by the polarizing separation film 25 and light which has beenreflected by the reflection means 29 in given directions, respectively,and they are preferably made of a metal material having high reflectancesuch as Ag, Au, and Cu or of a plurality of dielectric materials havingvarious refractive indices.

A diffusion angle converting (light beam diameter changing rate alongbeam axis adjusting) means 31, which is formed on the third inclinedplane 22 c of the first substrate 22 d, changes a diffusion (light beamdiameter changing) angle of light in the luminous flux reflected by thereflection means 30, in other words, light reflected by the low-densityoptical disk 19 from a diffusion direction to a convergence directionand reflects directly light in a convergence direction, in other words,the luminous flux reflected by the high-density optical disk 18.

The diffusion angle converting means 31 is preferably made of adiffraction grating, particularly a reflection-type hologram since itcan transmit light very efficiently. Particularly as the reflection-typehologram, it is preferable to use one having a cross section in a shapeof a staircase of four or more steps or having a serrated cross sectionsince the light can be used very efficiently and the quantity of lightcan be prevented from being decreased.

In this embodiment, the reflection-type hologram 31 is formed to reflectmost of the luminous flux composed of light emitted from the lightsource 2 as zero-dimensional light and to diffract most of the luminousflux composed of light emitted from the light source 9 to plusone-dimensional light. With this configuration, it is possible to avoida problem that it is hard to detect RF signals or to form focusing ortracking signals due to a divergence of the luminous flux from the lightsource 9 on the light receiving means 21 caused by a forward (from therecord medium) shift of the luminous point of the light emitted from thelight source 9, and therefore a high-performance optical pickup can beactualized so as to form precise signals reliably.

A signal formation means 32, which is placed on an end surface of thesecond substrate 22 e in the side of the light sources, has aconfiguration so as to guide the light guided from the diffusion angleconverting means 31 into a predetermined position of the light receivingmeans 21 and to give predetermined characteristics to the incidentluminous flux to form focusing or tracking signals.

A light receiving means 33, which is placed on a side of the firstsubstrate 22 d at almost the same height as for the filter 24 or themeans for forming a plurality of beams 28, controls outputs of the lightsource 2 and the light source 9 by receiving reflected light withoutpassing through the filter 24 in the light emitted from the light source2 and transmitted light without being reflected by the filter 24 in thelight emitted from the light source 9 and then returning the signals asfeedback to power supply control circuits of the light source 2 and thelight source 9.

With this configuration to guide both of a part of forward emitted lightemitted from the light source 2 and then guided to the record medium anda part of forward emitted light emitted from the light source 9 and thenguided to the record medium to the light receiving means 33, the samelight receiving means 33 is used for monitoring in both of operations ofthe high-density optical disk 18 and the low-density optical disk 19. Inother words, only one light receiving means is needed for monitoring,and therefore the number of components can be reduced.

In addition, with the light receiving means 33 integrated with anoptical head containing the plurality of light sources 2 and 9 and thelight receiving means 21, a space for an arrangement of the lightreceiving means 33 can be omitted from the optical pickup, so as todownsize the optical pickup. Furthermore, the light receiving means 33can be positioned to the light sources 2 and 9 easily and veryprecisely, and therefore productivity of the optical pickup can beincreased and a quantity of output light from the light sources can becontrolled accurately.

Furthermore, only by installing the optical head for which positioningis completed among respective members into the carriage with adjustmentsof flyer and rotation directions, a positioning process at an opticalpickup assembly can be largely simplified, and therefore productivity ofthe optical pickup can be significantly increased.

Next, an explanation will be made for why the optical member 22 isformed by two components, the first substrate 22 d and the secondsubstrate 22 e. The first substrate 22 d has a plurality of inclinedplanes, on which various optical elements are arranged in parallelpositions. Accordingly, various optical elements on the first substrateare arranged being inclined to the optical axis of the incident light.Therefore, if an optical element having a high dependence on angles suchas a hologram is formed on the first substrate 22 d, a tolerance byangles is increased unless positioning is performed at an extremely highprecision, which leads to a very high possibility of degradingcharacteristics of light toward the record medium. It also leads todegrading signal characteristics, which unfavorably results in a causeof decreasing the performance of the optical pickup device. Accordingly,in this embodiment, the diffusion angle converting means 23 and 27 whichseem to be highly dependent of angles are formed on the second substrate22 e which is formed separately from the first substrate 22 d, so thatthe diffusion angle converting means 23 and 27 are placed almostperpendicularly to the optical axis of the light emitted from the lightsource 2 and the light source 9, respectively.

With this arrangement, it is possible to prevent the characteristics oflight guided to the record medium from being degraded almost completely,so as to provide a high-performance optical pickup device with lessdegradation of signal characteristics favorably.

Various optical elements arranged on the second substrate 22 e arepreferably formed only on one side of the second substrate 22 e.

This is because these optical elements are formed in a physical orchemical method such as etching via a mask in a given shape, andtherefore a single-side formation is effective to reduce the number ofmasks and the number of etching times, whereby the number of processescan be decreased, too. In addition, it does not need to turn back amaster of the substrate 22 e, and therefore it is possible to omit aplurality of times of positioning. Therefore, productivity can begreatly increased and a manufacturing cost be reduced.

In this embodiment, the diffusion angle converting means 23 and 27 andthe signal formation means 32 are formed on the end surface 22 f of thesecond substrate 22 e in the side of the light sources.

Further in this embodiment, the light sources 2 and 9 are placed so asto be opposite to the second substrate 22 e. In other words, in thisconfiguration, the light emitted from the light sources 2 and 9 isincident on the surface 22 f of the second substrate 22 e and convertedto luminous flux having given characteristics by various opticalelements formed on the optical member 22 so as to be guided to therecord medium.

With this configuration, the light sources 2 and 9 can be positionedwith the surface 22 f of the second substrate 22 e in the side of thelight sources being considered as a reference area. In other words, theplurality of light sources can be positioned with a single referencearea, whereby the light sources 2 and 9 can be positioned to variousoptical elements formed on the optical member 22 more precisely, andtherefore it becomes possible to prevent a degradation of opticalcharacteristics caused by a deviation of the positions of the lightsources 2 and 9 to various optical elements on the optical member 22. Inaddition, the positioning between the light source 2 and the lightsource 9 can be easily performed due to the single reference area.

Accordingly, there is almost no deviation of positions between lightsources or between a light source and an optical element, so as toachieve a very reliable optical pickup having favorable opticalcharacteristics.

In this embodiment, a distance between the surface 22 f opposite to thelight sources of the second substrate 22 e and the light source 2 isequal to that between the surface 22 f and the light source 9. With thelight sources 2 and 9 arranged in this relationship, the light sources 2and 9 can be fixed to, for example, an identical parallel plane memberwith being put on it, and therefore the height precision of the lightsources 2 and 9 can be easily secured. Accordingly, it is possible toprevent a degradation of optical characteristics caused by relativelylower height precision, so as to achieve an optical pickup havingfavorable record or reproduction characteristics.

Further in this embodiment, the light source mounting portion 34 has arectangular parallelepiped or plate shape with the light sources 2 and 9mounted on its top or side. The light source mounting potion 34, whichis put on the substrate portion 20 a or the sidewall portion 20 b as aseparate member or a part of the substrate portion 20 a or the sidewallportion 20 b, dissipates the heat generated by the light sources 2 and 9in addition to holding the light sources 2 and 9.

With this configuration in which the plurality of the light sources aremounted on the same light source mounting portion, the light sources 2and 9 can be previously fixed in a predetermined relationship ofpositions to the light source mounting portion 34, and therefore inassembling the optical head, positioning between the optical member 22and the light sources 2 and 9 can be performed easily and precisely, soas to increase productivity of the optical head. In addition, thislimits an occurrence of a deviation of the positions between the lightsources 2 and 9 and the optical member 22, so as to achieve an opticalpickup having superior optical characteristics.

Furthermore, with the light sources 2 and 9 arranged on the same surfaceof the light source mounting portion 34, the light sources 2 and 9 canbe installed on the light source mounting portion 34 more easily, and incomparison with a configuration in which they are arranged on differentsurfaces, the light sources 2 and 9 can be easily connected toelectrodes for supplying power to them or ground with wiring. Inaddition, relative positioning between the light sources 2 and 9 canalso be performed easily and precisely.

Still further, although areas in the light source mounting portion onwhich the light sources are mounted must be chamfered at an extremelyhigh precision, only one area is to be chamfered by arranging theplurality of the light sources on the same area, whereby themanufacturing processes can be reduced and therefore the productivitycan be increased in addition to a decrease of a production cost.

Materials of the light source mounting portion 34 are almost the same asfor the light source mounting portions 150 and 152 in the firstembodiment, and the explanation is omitted here.

Next, an explanation will be made for a method of supplying power to thelight sources 2 and 9 with reference to the accompanying drawings.Referring to FIG. 8, there is shown an enlarged view of a neighborhoodof light sources of the second embodiment according to the presentinvention. The light sources 2 and 9 are arranged almost in parallel onan end surface 34 a of the light source mounting portion 34 andelectrodes 36 a, 36 b, and 36 c are also placed on it. The electrode 36a is used for supplying power to the light source 2, the electrode 36 bis for supplying power to the light source 9, and the electrode 36 c isused as a ground of the light sources 2 and 9.

A single terminal 37 a out of the plurality of terminals 20 c on thepackage 20 is used to supply power to the light source 2, anotherterminal 37 b out of remaining terminals 20 c is used to supply power tothe light source 9, and still another terminal 37 c out of furtherremaining terminals 20 c is used as a ground.

The terminal 37 a and the electrode 36 a are electrically connected witheach other via a connecting member 38 a such as wire bonding, andfurther the electrode 36 a is electrically connected to the top of thelight source 2 via a connecting member 38 c such as wire bonding in thesame manner. Additionally, the terminal 37 b and the electrode 36 b areelectrically connected with each other via a connecting member 38 b suchas wire bonding, and further the electrode 36 b is electricallyconnected to the top of the light source 9 via a connecting member 38 dsuch as wire bonding in the same manner. Further, the electrode 36 c isformed from the end surface 34 a of the light source mounting portion 34to the bottom 34 b facing the substrate portion 20 a, so as to have aconfiguration in which the electrode 36 c is electrically connected tothe terminal 37 c automatically by bonding the substrate portion 20 a tothe light source mounting portion 34 by means of solder or a bondingmaterial having conductivity such as conductive resin.

With the electrodes 36 a and 36 b, which are power supply points to thelight sources 2 and 9, placed on the same plane in this manner, theconnection between the electrode 36 a and the terminal 37 a can beperformed simultaneously with the connection between the electrode 36 band the terminal 37 b without rotating the light source mounting portion34, and therefore workability and productivity can be improved inconnecting processes. In addition, with forming a plane almost inparallel with an end surface on which electrodes 36 a and 36 b areplaced at the points to which the terminals 37 a and 37 b are connectedand bonding this plane to the electrodes, respectively, angles of thebonded plane need not be adjusted so as to improve workability atbonding as well as reliability at bonding. If these planes are formed inalmost the same plane, a moving distance of the bonding device can beminimized at the bonding so as to further improve an efficiency of thework.

Preferably the light sources 2 and 9 are also formed on the same planeas for the electrodes 36 a and 36 b, whereby the connection between theelectrodes and the light sources can be performed more easily, andtherefore assembling workability of the optical pickup can be furtherimproved.

The electrodes 36 a and 36 b are preferably formed on end portions ofthe end surface 34 a of the light source mounting portion 34,respectively. This configuration makes it possible to minimize both ofthe distances of the connections between the terminal 37 a and theelectrode 36 a and between the terminal 37 b and the electrode 36 b, andtherefore it is possible to prevent an occurrence of disadvantages suchas a short-circuit caused by connecting members 38 a and 38 b brought incontact with other members having conductivity, a broken connectingmember which is too long, or an electrode or a terminal coming off abonded site.

Although the electrodes 36 a and 36 b and the light sources 2 and 9 arearranged on the same plane in this embodiment, the electrodes may beformed on two planes. For example, as shown in FIG. 9, the electrodesare formed on two planes, the top 34 c of the light source mountingportion 34 and the end surface 34 a thereof, a part on the top of theterminal 37 a is connected with a part on the top 34 c of the electrode36 a via the connecting member 38 a, and a part on the top of theterminal 37 b is connected with a part on the top 34 c of the electrode36 b via the connecting member 38 a. This configuration makes itpossible to decrease the number of the connection points existing on thesame plane, which prevents disadvantages almost completely such asdamaging the connecting member 38 c by mistake when installing theconnecting member 38 a, and therefore a yield of the optical pickup canbe improved. The angular portions of the light source mounting portionon which the electrodes are mounted over the two planes are preferablyrounded at a predetermined radius (R), since it prevents the electrodesfrom being damaged by the angular portions so as to maintain a reliableelectric contact of the electrodes formed on the respective planes. Inthe same manner, it is preferable to round the angular portions of theend surface 34 a on which the electrode 36 c is formed and the bottom 34b.

Next, for a backward emitting light of the light sources 2 and 9, areflection, a light absorption, or a scattering member is arranged inthe same manner as for the light sources 2 and 9 in the firstembodiment. Either one reflection member can be installed in each of thelight source 2 and the light source 9, or totally one reflection membercan be installed for a plurality of light sources.

Referring to FIG. 10, there is shown an enlarged view of a neighborhoodof the light sources of the second embodiment according to the presentinvention.

A reflection member 35 is mounted on the substrate 20 a of the package20; a plane 35 a opposite to the end surface 2 i on which the luminouspoint 2 g of the light source 2 is present is arranged being inclinedtoward the side of the light source 2, and a plane 35 b opposite to anend surface 9 i on which the luminous point 9 g of the light source 9 ispresent is arranged being inclined toward the side of the light source9.

As a material of the reflection member 35, it is preferable to use ametallic material having a high reflectance or to form the reflectionmember 35 with a low-cost material having a low reflectance beforeforming a metallic or dielectric film having a high reflectance over theplanes 35 a and 35 b or only on a portion on which light is incident.

The angles of inclination of the planes 35 a and 35 b of the reflectionmember 35 are preferably set according to the diffusion angles of thelight emitted from the light source 2 and the light source 9. In otherwords, for example, if a degree of the diffusion angle of the lightemitted from the light source 2 is greater than that of the diffusionangle of the light emitted from the light source 9, an angle ofinclination (1 of the plane 35 a which is greater than an angle ofinclination (2 of the plane 35 b makes it possible to prevent not onlylight from the light source 9 having a low diffusion angle but alsolight from the light source 2 having a high diffusion from beingincluded into a predetermined optical path of the optical member 22 orthe light receiving elements, whereby an occurrence of stray light canbe significantly limited, so as to achieve an optical pickup havingfavorable signal characteristics.

Both of the angle of inclination of the plane 35 a and the angle ofinclination of the plane 35 b set to ⊖2 makes it possible to limit thenumber of the settings of the inclined planes to a single time to formboth planes in a manufacturing process of the reflection member 35 whilerestraining an occurrence of stray light significantly, and therefore itis possible to improve the productivity and to reduce the cost due tothe simplified manufacturing process.

Furthermore, the angles of inclination are preferably set, taking intoconsideration also distances between the light source 2 and thereflective surface 35 a and between the light source 9 and thereflective surface 35 b.

Although the planes 35 a and 35 b of the reflection member 35 areinclined in an xy direction in FIG. 10 in this embodiment, they may beinclined in a yz direction toward the opposite direction of the lightsource mounting portion 34.

With this configuration, the inclined planes can be arranged on a singlesurface of the reflection member 35, so as to increase the productivityof the reflection member 35.

Although the planes 35 a and 35 b of the reflection member 35 are formedso as to have high reflectance, a high extinction modulus may be appliedinstead of the high reflectance in the same manner as for the firstembodiment.

Further, it is most preferable to have a configuration in which thelight reflected by the planes 35 a and 35 b is discharged to the outsideof the package 20 from an opening other than the opening 20 d on thesidewall portion 20 b of the package 20. This configuration makes itpossible to discharge the backward emitting light from the light sources2 and 9 to the outside of the package 20 almost completely, so as tosignificantly decrease the possibility of an occurrence of stray lightcaused by the backward emitting light. In this embodiment, the openingis preferably covered by a transparent member such as glass or resin,since it is effective to prevent a degradation caused by the lightsources or the light receiving elements in contact with an air ormoisture.

Although the backward emitting light from the light source 2 or 9 isreflected or absorbed by the reflection member 35 in this embodiment,there may be used a configuration in which, instead of the reflectionmember 35, cutouts are arranged so as to have predetermined angles ofinclination to the end surfaces 2 i and 9 i of the light sources 2 and 9in portions opposite to the light sources 2 and 9 of the substrateportion 20 a so that the light from the light sources 2 and 9 isreflected or absorbed by a reflective or light absorbent surface placedin the cutout portions. With this configuration, the reflective or lightabsorbent surface can be arranged in the substrate portion 20 a, andtherefore the reflection member 35 can be omitted so as to decrease thenumber of the components and to simplify assembling processes of theoptical pickup.

Further, with the light absorbent surface arranged on the surface of thesubstrate portion 20 a which is opposite to the light sources withoutcutouts on the substrate portion 20 a, backward emitting light from thelight sources 2 and 9 can be absorbed, whereby stray light can berestrained. In this configuration, both of the reflection member 35 andthe cutouts of the substrate portion 20 a need not be arranged, andtherefore the manufacturing process of the substrate portion 20 a can besimplified and the number of the components be decreased, which leads toincreasing the productivity of the optical pickup and to lowering thecost easily.

As set forth hereinabove, with the configuration in which light from theplurality of the light sources contained in an identical package iscaused to be incident on the optical member having the plurality of theoptical elements so as to be guided to almost the same optical path, theoptical elements or other components can be condensed to a single unitthough they are conventionally arranged for each light source, andtherefore the entire optical pickup can be significantly downsized incomparison with the optical pickup whose respective light sources arearranged separately and the positioning between respective opticalmembers and respective light sources is unnecessary, whereby theproductivity is greatly increased and further installation errorsbetween the respective optical elements can be decreased to the minimum,and therefore favorable optical characteristics can be achieved and aloss of light caused by installation errors between respective opticalelements can be minimized, by which an optical pickup having a favorableefficiency of utilizing light can be obtained. Furthermore, it does notneed to form a plurality of optical systems corresponding to a pluralityof the light sources, respectively, by using an optical member, wherebyit is possible to increase the productivity due to a decrease of thenumber of the components and to simplify the positioning of thecomponents.

With the configuration in which light from two light sources is guidedto an identical path in the optical member 22 bonded to the package 20,it requires less members for a unification into a single optical path incomparison with a configuration in which they are unified outside theoptical head, and therefore the number of the components can bedecreased and the processes required for positioning between the lightsources and these members be omitted, so as to achieve an optical pickuphaving a favorable productivity. Furthermore, due to a single opticalaxis of the light emitted from the optical member 20, it is possible tosuppress a decrease of the quantity of light on the light emittingsurface of the optical member 20 and to reduce portions in the lightemitting surface which requires surface grinding to prevent anoccurrence of an aberration in comparison with the configuration inwhich there are a plurality of axes of emitted light, whereby thegrinding processes can be simplified and a manufacturing time be reducedaccording to it.

Furthermore, with at least one of the light emitted from the lightsource 2 and the light emitted from the light source 9 being reflectedby the optical member 22 a plurality of times so as to be guided to apredetermined optical path, the optical member 22 can be downsized and alength of the optical path from the optical member 22 can be decreasedin comparison with a configuration in which the light is guided withoutreflection, and therefore it is possible to actualize a smaller andthinner optical pickup. As described in this embodiment, in theconfiguration in which the light from the light source 2 is emittedalmost in parallel with the light from the light source 9, anoptimization of an arrangement position in the optical member 20 and thenumber of reflection times makes the most ideal relationship between adistance from the light source 2 to the light emitting surface of theoptical member 20 and a distance from the light source 9 to the lightemitting surface, and therefore the optical characteristics in thisoptical pickup can be favorable without so much difference between theheight of the light source 2 and that of the light source 9 from thesubstrate portion 20 a. Accordingly, the size of the package can bereduced and therefore it can contribute to downsizing of an opticalpickup.

Still further, with different diameters of the light emitted from theoptical member 20 between luminous flux from the light source 2 andluminous flux from the light source 9, a diameter of the light incidenton the condenser 17 can be changed and therefore a convergence positionof the light from the light source 2 can be different from that of thelight from the light source 9. In other words, with a diameter of thelight which is incident on the condenser being differentiated betweenindividual light sources, it becomes possible to condense light to therecord mediums having different record area positions by using a singlecondenser so that the information can be recorded or reproduced. Inaddition, the same effects can be obtained by using different diffusionangles of the light incident on the condenser, and a further remarkabledifference can be obtained in the convergence position with acombination of different apertures for incident light and diffusionangles.

An explanation will now be made for an operation of an optical pickuphaving the configuration described above.

If the record medium is the high-density optical disk 18, light isemitted from the light source 2 for recording or reproduction. In thiscondition, the light emitted from the light source 2 is reduced in itsdiffusion angle by the diffusion angle converting means 23, in otherwords, an extent of the light is reduced.

This diffusion angle converting means 23 is effective to transmit moreof the light emitted from the light source 2 toward the high-densityoptical disk 18, and therefore it becomes possible to obtain efficientlya quantity of panel light on the high-density optical disk 18 which isparticularly required by a large amount for recording data. Accordingly,it is effective to provide an optical pickup which can be favorably usedfor both of recording and reproduction.

In addition, this configuration makes it possible to decrease the lightwhich may be included into portions other than a predetermined opticalpath of the optical member 22, which reduces components of stray lightin the optical member 22, and therefore it is also possible to preventstray light from being incident on the light receiving means 21 or thelike to degrade signal components.

The light whose extent is reduced by the diffusion angle convertingmeans 23 is transmitted through the filter 24 almost completely, alsotransmitted through the polarizing separation film 25 which is arrangedbehind it almost completely, and then incident on the color (chromatic)aberration correcting (compensating) means 501. The color (chromatic)aberration correcting (compensating) means 501 is set so as not to applya color (chromatic) aberration correction effect to the light emittedfrom the light source 2 almost at all, and therefore the incident lightis transmitted through the color (chromatic) aberration correcting(compensating) means 501 without any application of the effect of thecolor (chromatic) aberration correcting (compensating) means 501 almostat all, and then it is incident on the quarter-wavelength plate 26.

When passing through the quarter-wavelength plate 26, the light whichhas been a linear polarization until then is converted to a circularpolarization, and then if there is a collimator lens, it passes throughthe collimator lens 16 and is converted to parallel light before it isincident on the condenser 17, and otherwise, it is directly incident onthe condenser 17, and then the light is converged to the high-densityoptical disk 18.

Returning light which has been reflected by the high-density opticaldisk 18 is incident on the quarter-wavelength plate 26 again, and thenit is converted from the circular polarization to the linearpolarization which crosses at right angles to the polarization directionin which the light is emitted from the light source 2 when passingthrough the plate 26 and incident on the polarizing separation film 25.At this point, since the polarization direction is different from thatof the forward path, the light is reflected by the polarizing separationfilm 25 and incident on the diffusion angle converting means 31 via thereflection means 29 and 30. The light incident on the diffusion angleconverting means 31 is reflected without being diffracted almost at all,luminous flux having a predetermined shape is formed in a given positionon the light receiving means 21 by the signal formation means 32, and anRF signal and both of focusing and tracking signals are generated basedon the light incident on the light receiving means 21, so as toreproduce information and to perform an optimum control of the opticalpickup.

If the record medium is the low-density optical disk 19, light isemitted from the light source 9 for recording or reproduction. In thiscondition, in relation to the light emitted from the light source 9, thedirection of an extent of the light is changed from the diffusiondirection to the convergence direction, in other words, the light isconverted from diffused to converged light by the diffusion angleconverting means 27.

The light converted to the converged light by the diffusion angleconverting means 27 is divided to a plurality of beams by the means forforming a plurality of beams 28 to be reflected and incident on thefilter 24. Then, the light is reflected by the filter 24 almostcompletely, is transmitted through the polarizing separation film 25behind it almost completely, and then is incident on thequarter-wavelength plate 26.

When passing through the quarter-wavelength plate 26, the light whichhas been a linear polarization until then is converted to a circularpolarization, and then if there is a collimator lens, it passes throughthe collimator lens 16 so as to have a smaller diffusion angle before itis incident on the condenser 17, and otherwise, it is directly incidenton the condenser 17, and then the light is converged to the low-densityoptical disk 19. At this point, the diameter of the light incident onthe condenser 17 becomes smaller than that of the light from the lightsource 2.

Then, returning light which has been reflected by the high-densityoptical disk 19 is incident on the quarter-wavelength plate 26 again,and then it is converted from the circular polarization to the linearpolarization which crosses at right angles to the polarization directionin which the light is emitted from the light source 9 when passingthrough the plate 26 and incident on the polarizing separation film 25.At this point, since the polarization direction is different from thatof the forward path, the light is reflected by the polarizing separationfilm 25 and incident on the diffusion angle converting means 31 via thereflection means 29 and 30. The light incident on the diffusion angleconverting means 31 is reflected with being diffracted to plusone-dimensional light almost completely, and the light which has beendiffusion light before being incident is converted to converged light tobe incident on the signal formation means 32.

Luminous flux having a predetermined shape is formed in a given positionon the light receiving means 21 by the signal formation means 32, and anRF signal and both of focusing and tracking signals are generated basedon the light incident on the light receiving means 21, so as toreproduce information and to perform an optimum control of the opticalpickup.

If a plurality of light sources are arranged in different positions inthe same package as described above, the light emitted from respectivelight sources often generates a wavefront aberration significantlydifferent each other. To cope with this, an optimization is made fordistances between the luminous point 2 a of the light source 2 and thecollimator lens and between the luminous point 9 a of the light source 9and the collimator lens. It will now be explained below.

Referring to FIG. 11, there is shown a diagram of a relationship betweena luminous point in an infinite optical system and a collimator lens ofthe second embodiment according to the present invention. In FIG. 11,reference numeral L7 indicates an effective focal length between thecollimator lens 16 and a virtual luminous point 2 e, and referencenumeral L8 indicates an effective focal length between the collimatorlens 16 and a virtual luminous point 9 e. Additionally, referring toFIG. 12, there is shown a relationship between a wavefront aberrationamount in light and a distance ratio depending on a presence or absenceof a shift of the condenser of the second embodiment according to thepresent invention. In other words, when a ratio of L7 to L8 is changed,a wavefront aberration amount which is generated at an incidence on thecondenser is compared between a case in which the condenser 17 shifts by500 μm in a tracking direction (indicated by a thick line) and a case inwhich it does not shift in the tracking direction (indicated by a thinline). In general, a condenser under reproduction on an optical disk hasa possibility of shifting by a maximum of 500 μm in a trackingdirection. In addition, taking into consideration that it is assumedthat approx. 0.07λ (where λ indicates a wavelength of light) or lower ofa wavefront aberration amount as an RMS value is allowed to convergelight which has been incident on the condenser into the optical diskeffectively, and assuming that the wavefront aberration amount is 0.07λor lower at the maximum shift amount (500 μm) of the condenser 17 forthe light from the luminous point 9 a in which the aberration amount isrelatively large and the incidence conditions to the condenser 17 aresevere, light from both of the luminous points will converge on theoptical disk independent of the shift amount of the condenser 17 afterit is incident on the condenser 17. To satisfy this condition,apparently as shown in FIG. 12, the ratio of L7 to L8 (L8÷L7=H, it isdescribed hereinafter as, H) is preferably within a range of0.50<H<0.75.

Further, if the wavefront aberration amount is 0.04λ or lower as an RMSvalue under the same conditions, the light incident on the condenser 17is converged very precisely on the optical disk independently of a shiftamount of the condenser 17 whether the incident light is emitted fromeither luminous point 2 a or 9 a. To satisfy this condition, apparentlyas shown in FIG. 12, the ratio of L7 to L8 (H) is preferably within arange of 0.53<H<0.70 since it is effective to improve signalcharacteristics.

With an arrangement of the optical system so that the value of H iswithin the above range, the wavefront aberrations in every luminous fluxcan be theoretical threshold or lower values in an optical pickup havinga plurality of types of luminous flux in a single optical system, andtherefore every luminous flux can be condensed on the optical disk byusing a single condenser 17.

Accordingly, only one condenser 17 is needed for condensing, so that thenumber of condensers can be decreased and it is not required to arrangeany switching means for condensers, whereby it becomes possible todownsize an optical pickup, to increase the productivity due to adecrease of the number of the components, and further to improve thereliability of the optical pickup and to increase the operation speeddue to omission of a complicated mechanism.

Although an infinite optical system having the collimator lens 16 isused in this embodiment, a finite optical system may be used, too. If itis used, a space is not needed for arranging the collimator lens incomparison with the configuration in which the infinite optical systemis used, and therefore a size of the entire optical pickup can bereduced.

[Third embodiment]

A third embodiment of the present invention will be described below withreference to the accompanying drawings.

Referring to FIG. 13, there is shown a cross section of an integratedoptical head of the third embodiment according to the present invention,and referring to FIG. 14, there is shown a cross section of an opticalsystem of the third embodiment according to the present invention. Theorthogonal cross section in FIG. 14 illustrates an optical path with astraight line.

In FIGS. 13 and 14, a package 70 comprises a light source 2 for emittinglight for a high-density optical disk 18 and a light source 9 foremitting light for a low-density optical disk 19, a substrate portion 70a on which are mounted a light receiving means 91 for receiving lightreflected by the high-density optical disk 18, a light receiving means92 for receiving light reflected by the low-density optical disk 19 andthe like, and a sidewall portion 70 b arranged so as to enclose thesemembers.

The package 70 has almost the same configuration as for the package 20described in the second embodiment, and therefore explanation thereof isomitted here.

In addition, the light sources 2 and 9 contained in the package 70 arethe same as those for the second embodiment, and their explanation isomitted here, too.

Next, a first optical member 72 is used to guide light emitted from thelight sources 2 and 9 to a predetermined optical path and to guidereturning light which has been reflected by the optical disk to apredetermined optical path.

The first optical member 72 comprises a first inclined plane 72 a, asecond inclined plane 72 b, and a third inclined plane 72 c, preferablyhaving a configuration in which particularly a light incident surface isalmost in parallel with a light emitting surface and incident light oremitted light is incident almost perpendicularly on the surfaces ofthese planes. With this configuration, it is possible to suppress anoccurrence of a non-point aberration to the incident light, so as toprevent a degradation of optical characteristics of transmitted light.

Furthermore, various optical elements are formed on the first inclinedplane 72 a, the second inclined plane 72 b, and the third inclined plane72 c.

An explanation will now be made for various optical elements existing inthe first optical member 72.

First, on the first inclined plane 72 a, reflection films 73 and 74 areformed. The reflection film 73 is used to reflect light emitted from thelight source 2 in a given direction and the reflection film 74 is usedto reflect light emitted from the light source 9 in a given direction.As materials of the reflection films 73 and 74, preferably there is useda metal material having high reflectance such as Ag, Au, and Cu or aplurality of dielectric materials having various refractive indices in aplurality of alternate layers.

Although the reflection film 73 and the reflection film 74 areindividually arranged in this embodiment, they can be formed in a singlelarge reflection film almost all over the first inclined plane 72 a. Ifthis configuration is used, it is possible to omit a process of formingreflection films by using masks and to decrease the masks for formingthe reflection films, and therefore the productivity can be increasedand the manufacturing cost can also be reduced.

On the second inclined plane 72 b, polarizing separation films 75 and 76are formed. Light emitted from the light source 2 and reflected by thereflection film 73 is incident on the polarizing separation film 75, andlight emitted from the light source 9 and reflected by the reflectionfilm 74 is incident on the polarizing separation film 76. Thesepolarizing separation films 75 and 76 transmit light having specificpolarization directions and reflect light having other polarizationdirections.

These polarizing separation films 75 and 76 are preferably made of aplurality of dielectric materials having refractive indices differentfrom each other in a plurality of alternate layers since more precise PSseparation can be performed. Particularly in this embodiment, thepolarizing separation films transmit S polarization components emittedfrom the light sources 2 and 9 and reflect P polarization components.

The film thickness of the polarizing separation films 75 and 76 ispreferably set according to a wavelength of incident light. It decreasesan incompleteness of a polarizing separation caused by a differencebetween wavelengths of incident light so as to perform more precise PSseparation.

These polarizing separation films 75 and 76 are effective to guide lightto the record media without decreasing a quantity of transmitted lightalmost at all, and therefore it is possible to increase an efficiency ofutilizing light and to obtain a predetermined quantity of panel light onthe light sources 2 and 9 at small outputs so as to obtain longer livesof the light sources 2 and 9.

Although the polarizing separation films 75 and 76 are individuallyarranged in this embodiment, if there is only a small difference betweenwavelengths of incident light, they can be formed in a single largepolarizing separation film almost all over the top of the secondinclined plane 72 b. If this configuration is used, it is possible toomit a process of forming polarizing separation films by using masks andto decrease the masks for forming the polarizing separation films, andtherefore the productivity can be increased and the manufacturing costcan also be reduced.

Although the polarizing separation films are used as separation meansbetween the emitted light and returning light in this embodiment,instead of them, a half mirror or other separation means may be usedaccording to a required quantity of panel light.

Next, an explanation will be made for other optical members arranged onthe second inclined plane 72 b.

Reference numerals 77 and 78 indicate holograms for light of a monitor,and the hologram 77 reflects to diffract a part of the light emittedfrom the light source 2 and reflected by the reflection film 73 in agiven direction. The light reflected to be diffracted by this hologram77 is guided to a reflection section 79 mounted on the top of the firstoptical member 72, and then incident on a monitor light receivingsection on a light receiving means 91. Afterward, it drives a powersupply control circuit of the light source 2 based on an electric signalfrom the monitor light receiving section, adjusts the power to beapplied to the light source 2, and then controls the quantity of lightemitted from the light source 2 so as to always be an optimum value.

The hologram 78 reflects to diffract a part of the light emitted fromthe light source 9 and reflected by the reflection film 74 in a givendirection. The light reflected to be diffracted by this hologram 78 isguided to a reflection section 80 mounted on the top of the firstoptical member 72, and then incident on the monitor light receivingsection on a light receiving means 92. Afterward, it drives a powersupply control circuit of the light source 9 based on an electric signalfrom the monitor light receiving section, adjusts the power to beapplied to the light source 9, and then controls the quantity of lightemitted from the light source 9 so as to always be an optimum value.

Furthermore, reflection films 81 and 82 are put on a portion nearest tothe second inclined plane 72 b.

The reflection film 81 is used to reflect incident light which has beenreflected by an optical path dividing means 83 and to guide it to apredetermined position, and the reflection film 82 is used to reflectincident light which has been reflected by an optical path dividingmeans 84 and to guide it to a predetermined position. The reflectionfilms 81 and 82 are preferably made of a metal material having highreflectance such as Ag, Au, and Cu or of a plurality of dielectricmaterials having various refractive indices.

Lastly, the optical path dividing means 83 and 84 are formed on thethird inclined plane 72 c.

The optical path dividing means 83 transmits or reflects returning lightwhich has been emitted from the light source 2 and reflected by thehigh-density optical disk 18, and the optical path dividing means 84transmits or reflects returning light which has been emitted from thelight source 9 and reflected by the low-density optical disk 19. It ispreferable here to use a half mirror so that the quantity of transmittedlight is almost equal to that of reflected light in both of the opticalpath dividing means 83 and the optical path dividing means 84.

Next, the second optical member 86 will be described below.

The second optical member 86 is arranged so as to close the opening 70 dput on the sidewall portion 70 b of the package 70, with being bonded tothe sidewall portion 70 b of the package 70 by means of UV lighthardening resin, epoxy resin, or bonding glass. The second opticalmember 86 comprises a first substrate 86 a and a second substrate 86 b.These substrates are sequentially described below.

First, the first substrate 86 a is made of a material having favorabletransparency such as glass or resin having a parallel plane shape, witha diffusion angle converting means 87 formed in a region through whichthe light from the light source 9 at the end surface in the side of theshield member 85. The diffusion angle converting means 87, which is soas to match the optical axis of the light emitted from the light source9 on an end surface of the first substrate 86 a in the side of the lightsource 9, is used to make negative a diffusion angle of the lightincident from the light source 9, in other words, to convert the opticalpath of the light emitted from the luminous point 9 a of the lightsource 9 to light having an optical path which is as if it were emittedfrom a position nearer to the low-density optical disk 19 in comparisonwith a visual position, and practically it shifts the luminous point inan approaching direction to the low-density optical disk 19. Itapparently shifts the luminous point of the light source 9 from the trueluminous point 9 a to an apparent luminous point 9 e, and thereforeshortens the optical path from the light source 9 to the record medium.

The diffusion angle converting means 87 is preferably formed almostperpendicularly to the optical axis of the light emitted from the lightsource 9. In general, preferably an optical axis of incident lightprecisely matches a central axis of the diffusion angle converting means87. Some deviation, however, occurs frequently between them. To copewith this, the diffusion angle converting means 87 is formed almostperpendicularly to the optical axis of the light emitted from the lightsource 9, whereby it is possible to maximize a range of an amount ofdeviation between which the optical axis of incident light and thecentral axis of the diffusion angle converting means 87 is permitted, inother words, to maximize a tolerance of an amount of deviation to whicha degradation of the optical characteristics can be limited. Therefore,it is possible to lower a required precision for positioning between theoptical axis of incident light and the central axis of the diffusionangle converting means 87, whereby the positioning can be easilyperformed and time for the positioning can be reduced, too. In addition,to the contrary, if a deviation occurs between the optical axis of thelight and the central axis of the diffusion angle converting means 87, adegradation of the optical characteristics can be reduced. This leads topreventing a degradation of the optical characteristics caused by adeviation of a component with deterioration with age of bonding materialsuch as resin used for the bonding though it has been preciselypositioned initially, and therefore it is possible to achieve a veryreliable optical pickup having less degradation of opticalcharacteristics for a long period.

In addition, with the diffusion angle converting means 87 formed on theend surface closer to the light source 9 of the second optical member86, the diffusion angle converting means 87 exposed onto the surface ofthe second optical member 86 can be contained in the package 70, andtherefore it is possible to suppress a degradation of the diffusionangle converting means 87 caused by an absorption of moisture oroxidation in dielectric, glass, resin, or other materials of thediffusion angle converting means 87. Accordingly, a diffusion angle canbe precisely controlled for a longer period, and therefore thereliability of an optical pickup can be improved so as to actualize anoptical pickup maintaining superior optical characteristics for a longperiod.

From a viewpoint of a function as the diffusion angle converting means87, it is preferably made of a diffraction grating, particularly ahologram since it is effective to transmit light very efficiently.Particularly as a hologram, it is preferable to use one having a crosssection in a shape of a staircase of four or more steps or having aserrated cross section since the light can be used very efficiently andthe quantity of light be prevented from being decreased.

Furthermore, the diffusion angle converting means 87 is preferably incontact with a material having a lower refractive index than that of thesecond optical member 86 on which it is placed. Particularly, if thediffusion angle converting means 87 is made of a hologram, a degree ofthe conversion of a diffusion angle in the diffusion angle convertingmeans 87 is increased as a pitch of each slot of the hologram isdecreased. At a fixed pitch, as a greater difference is generatedbetween the refractive index of the optical member on which thediffusion angle converting means 87 is mounted and that of the materialwhich the diffusion angle converting means 87 is contacted, the degreeof the conversion of the diffusion angle is increased.

The minimum pitch, however, is limited due to a process limitation, andcurrently it seems to be limited to approximately 1 μm as a profitableline. If the pitch is increased, the diffusion angle converting means 87can be manufactured more easily, and therefore it is possible toincrease the productivity, to simplify a manufacturing device used formanufacturing, to reduce a work time, and to decrease the manufacturingcost. Furthermore, it can be precisely manufactured, so as to obtainfavorable optical characteristics.

From this viewpoint, it is apparent that a greater difference betweenthe above refractive indices is more favorable. Particularly, asdescribed in this embodiment, the light emitted from the light source 9is brought into convergence once and the light diffused afterward isbrought into incidence on the condenser 17 in this configuration, and toobtain a 1 μm or greater pitch of the hologram composing the diffusionangle converting means 87, only a 0.35 or greater difference is neededbetween the refractive index of the material of the optical member andthat of the material in contact with the diffusion angle convertingmeans 87, and further as described later, to limit a ratio of a distancebetween the light source 2 and the collimator lens 16 to a distancebetween the light source 9 and the collimator lens 16 to a predeterminedvalue or lower and to maintain the pitch of the hologram at 1 μm orgreater, only 0.5 or greater difference is needed between the refractiveindex of the material of the second optical member 86 and the refractiveindex of the material in contact with the diffusion angle convertingmeans 87. As a substance satisfying these conditions, air is used inthis embodiment. The air is capable of being distributed uniformly amongfine pitches of the diffusion angle converting means 87 unlike a solidbody such as resin or liquid and its refractive index is extremely smallsuch as, for example, approximately 1, and therefore it is effective toprevent a degradation of the optical characteristics caused by adeviation of the distribution with satisfying the conditions.Particularly in a type of the air, an inactive gas is preferable sinceit is effective to prevent a degradation of various optical elementsmounted on the optical member caused by an oxidation. Further, an amountof deterioration with age in the optical member 86 on which thediffusion angle converting means 87 is mounted can be set to the samevalue as that of the optical member 72 contained in the package 70, andtherefore a life of the optical pickup can be lengthened.

Next, the configuration of the diffusion angle converting means will bedescribed with reference to the drawings.

Referring to FIG. 15, there is shown a cross section of the diffusionangle converting means of the third embodiment according to the presentinvention. In the diffusion angle converting means 87, patterns ofconcentric circles each having an uneven cross section with the pitchdecreased as approaching to the peripheral portion. The patterns areformed in dry-etching or the like. If light R is incident on thehologram pattern, zero-dimensional light 95 transmitted withoutdiffraction, plus one-dimensional diffraction light 96 depending on apitch, and minus one-dimensional light 97 are generated. In thisembodiment, to suppress the zero-dimensional light 95 and the minusone-dimensional light 96 and to intensify the plus one-dimensional light97, the patterns have a multi-stage shaped cross section in adiffraction direction. This multi-stage can be formed by preparing aplurality of mask patterns and repeating a resist exposure anddry-etching. This pattern is effective to suppress an occurrence of thezero-dimensional light 95 and the minus one-dimensional light 96, andtherefore the quantity of panel light and the quantity of light requiredfor detecting signals can be gained so as to use the light source 9 at alow output.

In this condition, the diffusion angle converting means 87 is guidedfrom the light source 9 and luminous flux emitted on the low-densityoptical disk 19 is made of a pattern larger than an aperture formed inthe diffusion angle converting means 87. On the diffusion angleconverting means 87, both of the emitted light and the returning lightare incident. Particularly, the backward light passes through an opticalpath different from that of the emitted light when the condenser 17 isshifted. If the diffusion angle converting means 87 is designed so as tomatch the aperture for the emitted light, an eclipse may occur, by whichthe quantity of light incident on the light receiving means 92 isdecreased, and therefore signals may be inhibited to be reproduced orprecise servo signals may not be generated. To avoid thesedisadvantages, the aperture is enlarged to a region where the returninglight may be incident so as to prevent an occurrence of the eclipse.

Next, the second substrate 86 b, which is arranged on the top of thefirst substrate 86 a and bonded to the first substrate 86 a by means ofbonding material such as optical hardening resin, epoxy resin, bondingglass or the like, is used to guide light emitted from the light source2 or the light source 9 and guided via the first optical member 72 andthe first substrate 86 a of the second optical member 86 to a givenoptical path and to guide the returning light reflected by the opticaldisk to a given optical path.

In the second substrate 86 b, it is preferable that particularly asurface on which light is incident and a surface from which light isemitted are almost perpendicular to the optical axis of the light andthe respective surfaces are almost in parallel with each other. In thisconfiguration, it is possible to suppress an occurrence of a non-pointaberration in incident light, so as to prevent a degradation of opticalcharacteristics of transmitted light.

Furthermore, the first inclined plane 86 d and the second inclined plane86 c are almost in parallel with each other, each having an inclinationin a direction different from that of the inclined plane formed on thefirst optical member 72.

On the first inclined plane 86 d and the second inclined plane 86 e,various optical elements are formed.

First, on the first inclined plane 86 d, means for forming a pluralityof beams 88 is arranged.

The means for forming a plurality of beams 88 includes a polarizingseparation film 88 a which reflects light along the polarizationdirection or transmits light and a beam separating section 88 b whichreflects incident light with separating it into a plurality of luminousflux, and the light emitted from the light source 9 and transmittedthrough the diffusion angle converting means 87 is transmitted throughthe polarizing separation film 88 a almost completely and then incidenton the beam separating section 88 b. Then, the incident light isseparated into a plurality of luminous flux by the beam separatingsection 88 b and then reflected.

The beam separating section 88 b is preferably made of a diffractiongrating since it is effective to form a plurality of luminous fluxefficiently. In this embodiment, it has a configuration in which threetypes of luminous flux are mainly formed; zero-dimensional light andplus and minus one-dimensional light generated in the diffractiongrating.

In this embodiment, the beam separating section 88 b also serves as adiaphragm to the light from the light source 9. Further in thisembodiment, light from both of the light sources 2 and 9 is caused to beincident on a single condenser 17, and an incidence pupil of thecondenser 17 is adjusted so that the light from the light source 2 isfocused on a record area of the high-density optical disk 18.Accordingly, in this condition, the condenser 17 is adjusted in itsshape and material so that the light from the light source is condensedon the record area of the high-density optical disk 18.

By means of this condenser 17, to cause the light from the light source9 to focus on the record area of the low-density optical disk 19, adiameter of the light from the light source 9 incident on the condenser17 is adjusted so as to be smaller than a diameter of the light from thelight source 2 in this embodiment. In general, a lens has more intensivecondensing application in the peripheral portion than in the centralportion. Accordingly, if light is expanded at incidence, it focuses on anearer position; if the light is not expanded so much at incidence, itfocuses on a farther position. In this embodiment, since the record areaof the low-density optical disk 19 is placed in a farther position thanthe record area of the high-density optical disk 18, it becomes possibleto condense the light from the light source 9 on the record area of thelow-density optical disk 19 by the condenser 17 which is designed withbeing adjusted to the light from light source 2 by optimizing theincidence aperture to the condenser 17 for the light from the lightsource 9.

This incidence aperture is adjusted by the beam separating section 88 b.In other words, the size of the beam separating section 88 b is adjustedso that the light reflected by the beam separating section 88 b has apredetermined diameter on the condenser 17.

With the beam separating section 88 b having this diaphragm function, adiameter of the light emitted from the light source 9 can be preciselyadjusted, and therefore a diameter of the light incident on thecondenser 17 can be set to a predetermined size, whereby the light fromthe light source 9 can be condensed on the record area of thelow-density optical disk 19 by the condenser 17. Furthermore, incomparison with a configuration in which the diaphragm is arrangedindividually, the number of the components can be decreased and it ispossible to omit time and labor of positioning between the diaphragm andthe light source 9, and therefore the productivity of an optical pickupcan be increased.

Further, with the diaphragm arranged in this position, light which isnot reflected by the beam separating section 88 b in the light emittedfrom the light source 9 directly passes through the first inclined plane86 d and then it is discharged to the outside of the optical member 86,and therefore it is possible to prevent the light which has not beenreflected from becoming stray light in the package 70.

Still further, while the emitted light toward the low-density opticaldisk 19 is transmitted through the polarizing separation film 88 a andthen incident on the beam separating section 88 b, the returning lightreflected by the low-density optical disk 19 is reflected by thepolarizing separation film 88 a, and therefore almost no light isincident on the beam separating section 88 b in this configuration. Withthe beam separating portion 88 b of the means for forming a plurality ofbeams 88 having the diaphragm function in this configuration, forexample, even if an optical axis of returning light is deviated from agiven position due to a shift of the condenser 17, almost no light isincident on the beam separating portion 88 b having the diaphragmfunction, whereby it is possible to prevent problems such as a decreaseof the quantity of light incident on the light receiving means caused byan interruption of the light intrinsically to be incident on the lightreceiving means by the diaphragm or an unbalanced distribution of thequantity of light. Therefore, favorably not only more precise RF signalscan be obtained, but also focusing or tracking servo signals can begenerated more precisely.

In addition, since the diaphragm can be placed in a position which is inboth of the optical path of the emitted light and that of the returninglight, an efficiency of utilizing a space in the optical pickup can beimproved. In other words, it is unnecessary to have another optical pathfor returning light so as not to pass through the diaphragm, andtherefore further downsizing of an optical pickup can be actualizedfavorably.

Furthermore, this beam separating section 88 b is placed on the opticalpath through which the light from the light source 9 passes, and thelight from the light source 9 is incident on the section 88 b while thelight emitted from the light source 2 toward the high-density opticaldisk 18 is not incident on the section 88 b, and therefore the diaphragmfor the light from the light source 9 does not interrupt the light formthe light source 2 nor give any bad influence. Therefore, particularlyin an optical pickup having a configuration in which a plurality oflight sources are contained in a single package and in which light fromthe plurality of the light sources is condensed to a predeterminedposition by a single condenser, the light from the plurality of thelight sources can be caused to be incident on the condenser at apredetermined diameter without any bad influence upon each light fromthe plurality of the light sources favorably.

A plurality of luminous flux generated here is applied in a givenposition of a track of the low-density optical disk 19, and then thequantities of the returning light are compared with each other, so as tobe applied to a tracking method commonly called a three-beam method fortracking on the low-density optical disk 19.

Unless the three-beam method is used as a tracking method, instead of anarrangement of the beam separating portion 88 b, a diaphragm film simplyhaving a diaphragm function is arranged, so as to have a function, notas a means for forming a plurality of beams, but as a diaphragm means.

On the second inclined plane 86 e, is formed a filter 89 having awavelength selectivity. The filer 89 transmits approximately 80% or moreof the light guided from the light source 2 and reflects approx. 80% ormore of the light guided from the light source 9.

With this filter 89 formed on the second inclined plane 86 e, the lightintroduced from the light source 9 can be reflected without interruptingthe light emitted from the light source 2 almost at all, and thereforethe light emitted from the light sources 2 and 9 can be introduced tothe record mediums at a high percentage. Therefore, it is possible toperform recording or reproduction to or from the record mediums withoutincreasing the quantity of light emitted from the light sources 2 and 9,which leads to preventing a reduction of the lives of the light sources2 and 9 caused by using the light sources 2 and 9 at a high outputpower. Furthermore, since the light sources 2 and 9 can be used at a lowoutput power, the temperatures of the light sources 2 and 9 are hardlyincreased, and therefore oscillation wavelengths of the light sources 2and 9 do not shift almost at all. Accordingly, it is possible to providea high-performance optical pickup which is capable of focusing moreprecisely.

By means of the second substrate 86 b, the light from the light source 2and that of the light source 9 are guided to almost an identical opticalaxis.

The optical path from an incidence of the light from the light source 9on the second optical member to an incidence of the light on the filter89 after being reflected by the means for forming a plurality of beams88 is formed so as to progress almost perpendicularly to the planeincluding the optical axis of the light passing through the firstoptical member 72.

Reference numeral 90 indicates a quarter-wavelength plate, and thequarter-wavelength plate 90 converts polarization directions of both ofthe light emitted from the light source 2 and transmitted through thefilter 89 and the light emitted from the light source 9 and reflected bythe filter 89 from a linear polarization to an elliptic polarization.

The quarter-wavelength plate 90 can be formed in a shape of a planarplate having a given thickness as shown in this embodiment or in a thinfilm.

A light receiving means 91 receives light transmitted through theoptical path dividing means 83 and light reflected by the optical pathdividing means 83 and then reflected by the reflection film 81, and alight receiving means 92 receives light transmitted through the opticalpath dividing means 84 and light reflected by the optical path dividingmeans 84 and then reflected by the reflection film 82. Both of theminclude a required number of various light receiving portions eachhaving a required shape in a required position for generating RFsignals, monitor signals, and tracking and focusing signals.

In this embodiment, the light receiving means 91 and the light receivingmeans 92 are arranged in almost an identical plane on the substrateportion 70 a of the package 70, and further so that the longer directionof the substrate portion 70 is almost in parallel with the longerdirection of the light receiving means 91 and the light receiving means92.

In this manner, with the plurality of light receiving means formedalmost in parallel with each other, it is favorably possible to minimizethe space in which the light receiving means are arranged in an opticalpickup in comparison with a configuration in which they are arranged invarious positions so as to downsize the optical pickup efficiently. Inaddition, with an identical surface in the package used for arrangementof the plurality of light receiving means, only one surface is requiredto be chamfered to obtain precise parallelism, so as to simplify thechamfering work, whereby an optical pickup having favorable productivitycan be achieved.

Although the light receiving means 91 and 92 are directly mounted on thesubstrate portion 70 a in this embodiment, the light receiving means maybe mounted, for example, via a member such as a light receiving meansarrangement plate on the substrate portion 70 a.

Next, a detailed description will be made for the arrangement of thelight receiving sections in the light receiving means 91 and 92.

Referring to FIG. 16, there is shown an arrangement of the lightreceiving means of the third embodiment according to the presentinvention. In FIG. 16, the light receiving means 91, which receiveslight emitted from the light source 2 and then reflected by thehigh-density optical disk 18, comprises light receiving portions 91 a,91 b, 91 c, 91 d, 91 e, and 91 f. The light receiving means 92, whichreceives light emitted from the light source 9 and then reflected by thelow-density optical disk 19, comprises light receiving portions 92 g, 92h, 92 i, and 92 j.

Reference numerals 91 m and 92 m indicate light receiving portions formonitoring; the light receiving portion 91 m receives a part of thelight guided from the light source 2 separated by the hologram 77 formonitor light, the light receiving portion 92 m receives a part of thelight guided from the light source 9 separated by the hologram 78 formonitor light. Light current generated according to a quantity of lightreceived by the light receiving portions 91 m and 92 m is transmitted toa signal processing circuit including a light source driving circuit, inwhich the quantities of light emitted from the light sources 2 and 9 arekept to be a predetermined quantity of light to control the powersupplied to the light sources 2 and 9.

Since these light receiving means 91 and 92 include a current-voltageconverting circuit for converting light current generated in respectivelight receiving portion to voltage signals, a voltage comparator for acomparison to check that each positive electrode of the light source 2and 9 exceeds a reference voltage, an adder for adding signals fromrespective light receiving portions, and an analog switch for switchingrespective light receiving portions based on output signals from thevoltage comparator, all of which are formed in a semiconductor process,a configuration of a circuit in a rear stage can be simplified so as toreduce the number of times of connections to terminals or electrodesrequired for electric connections, and therefore it is possible tosuppress a reduction of yield caused by a defective bonding to theminimum.

Next, an explanation will be made for a signal generation method in thelight receiving means 91. The reflected light from the high-densityoptical disk 18 returns to the first optical member 72, the lighttransmitted through the optical path dividing means 83 reaches the lightreceiving means 91 before an image formation, and then an image isformed in a shape of a half moon on the light receiving portions 91 a,91 b, and 91 e as shown in FIG. 16. The light reflected by the opticalpath dividing means 83 forms an image before being reflected by thereflection film 81 and reaching the light receiving means 91, and thenforms a reflected image having a shape of a half moon on the lightreceiving portions 91 c, 91 d, and 91 f. The light current generated inrespective light receiving portions is converted to voltage signals bythe current-voltage converting circuit and then directly outputsimultaneously with being transmitted to the adder so as to form(Va+Vb+Vf) and (Vc+Vd+Ve). By taking a difference between these(Va+Vb+Vf) and (Vc+Vd+Ve), a focus error signal is generated. This focuserror signal is generated in the so-called spot size detection (SSD)method.

Va, Vb, Vc, and Vd are transmitted to the signal processing circuit inthe rear stage and then a track error signal is obtained by a comparisonof a phase difference between (Va+Vc) and (Vb+Vd). This track errorsignal is generated in a so-called different phase detection (DPD)method. In addition, by taking a difference between (Va+Vd) and (Vb+Vc),a track error signal can be also obtained (a push-pull method). Whichmethod is used depends on a type of a disk.

Then, a signal generation method in the light receiving means 92 will bedescribed below. The reflected light from the low-density optical disk19 returns to the first optical member 72, the light transmitted throughthe optical path dividing means 84 formed by the half mirror reaches thelight receiving means 92 before an image formation and then forms acircular image in the light receiving portions 92 g and 92 h as shown inthe drawing. The light reflected by the optical path dividing means 84forms an image before being reflected by the reflection film 82 andreaching the light receiving means 92, and then forms a circular imagereversed to the light transmitted through the optical path dividingmeans 84 on the light receiving portions 92 g and 92 h. The light fromthe light source 9 is previously divided into three beams by the meansfor forming a plurality of beams 88, and therefore it is divided by theoptical path dividing means 84 so as to form circular images on thelight receiving portions 92 i and 92 j in the same manner. Light currentgenerated in respective light receiving portions is converted to voltagesignals by the current-voltage converting circuit. By taking adifference between the formed Vg and Vh, a focus error signal isgenerated in the spot size detection method in the same manner as forthe high-density optical disk 18. By taking a difference between Vi andVj, a track error signal (a three-beam method) is obtained.

With the light receiving portion in the light receiving means 91 havinga different shape from that of the light receiving portion in the lightreceiving means 92 and the different generation methods applied to ageneration of various signals in respective light receiving means inthis manner, even if shapes of incident light are not identical, thelight receiving portions can be arranged in positions appropriate torespective shapes of incident light, and therefore it is possible togenerate more precise focusing and tracking signals or RF signals.Furthermore, more precise focusing and tracking control can be performedin an optical pickup which is capable of recording or reproduction to aplurality of record mediums, and therefore it is possible to reduce aperiod of time in which data cannot be read or written due to adeviation from a predetermined track and to reduce a period of time inwhich information cannot be recorded or reproduced due to unfocusedlight beam on the record mediums. Accordingly, a period of time forreading or writing data can be reduced so as to achieve an opticalpickup having high access speed.

In addition, with a configuration in which a part of the forwardemitting light emitted from light source 2 and then guided to the recordmedium is guided to the light receiving portion 91 m for monitoringformed in the light receiving means 91 including the light receivingportions for receiving the RF signals or focusing or tracking signalsand in which a part of the forward emitting light emitted from lightsource 9 and then guided to the record medium is guided to the lightreceiving portion 92 m for monitoring formed in the light receivingmeans 92 including the light receiving portions for receiving the RFsignals or focusing or tracking signals, the number of the lightreceiving elements can be decreased in comparison with a configurationin which the light receiving means for monitoring is mounted on each ofthe light receiving means 91 and the light receiving means 92,separately.

Further, with a light receiving portion for monitoring arranged in thelight receiving means 91 and 92 including the light receiving portionsfor RF signals and for focusing and tracking signals, the lightreceiving portions for RF signals and for focusing and tracking signalsand the light receiving portion for monitoring are formed in apredetermined positional relationship in a step of manufacturing thelight receiving means 91 and 92, and therefore positioning between thelight receiving portion for monitoring and the light sources 2 and 9 canbe performed simultaneously with the positioning between the lightreceiving means 91 or 92 and the light source 2 or 9. Accordingly, thenumber of times of positioning in a production process can be decreasedso as to improve easiness of connections with the terminals, andtherefore it is possible to increase the productivity of an opticalpickup and to save spaces in comparison with a configuration in whichthe light receiving portion for monitoring is mounted on a semiconductorsubstrate other than the light receiving portion for RF signals and thelight receiving portion for the focusing and tracking signals, so as toactualize further downsizing of an optical pickup.

Furthermore, the light receiving means 91 and 92 are formed on an almostidentical plane on the substrate portion 70 a, and therefore the size ofthe optical pickup can be reduced in its thickness direction, whereby itis possible to make an optical pickup thinner.

Still further, with the light receiving portion for the monitor beinginstalled in the optical head in which the light sources 2 and 9 and thelight receiving means 91 and 92 are integrated, the light receivingportion for monitoring being installed in the sealed optical head inwhich an inactive gas is enclosed, it is possible to preventdisadvantages, for example, that the light receiving portion formonitoring is oxidized since it is put in contact with an air or thatits characteristics are degraded since it absorbs moisture, and to omita space for installing the light receiving portion for monitoring fromthe optical pickup, so that an optical pickup can be downsized.

This configuration only requires an installation into a carriage of theoptical head in which positioning between respective members iscompleted, with adjustments of a flyer and a rotational direction, andtherefore a positioning process at assembling the optical pickup can begreatly simplified, so that the productivity of the optical pickup canbe significantly increased.

Although the light receiving portion for monitoring is installed in bothof the light receiving means 91 and the light receiving means 92 in thisembodiment, it may be installed only one of the light receiving means 91and 92. If it is so, as shown in the second embodiment, the same lightreceiving portion is used for monitoring whether it is during anoperation of the high-density optical disk 18 or during an operation ofthe low-density optical disk 19. In other words, only one lightreceiving portion is required for monitoring, so as to decrease thenumber of the components.

In addition, light receiving means other than the light receiving means91 and 92 may be mounted on almost the same plane as for the lightreceiving means 91 and 92, so as to be used as light receiving means formonitoring.

Further, although two light receiving means 91 and 92 are arranged asthe light receiving means in this embodiment, all the light receivingmeans can be put together to be mounted on a single semiconductorsubstrate. If this configuration is applied, it is possible to decreasenot only the number of the components of the light receiving means, butalso the number of the positioning of the light receiving means, so asto achieve an optical pickup having a favorable productivity.

Next, a raised member formed in the light receiving means will bedescribed.

On the top of the light receiving means 91 and 92, raised members 190and 191 are mounted. These raised members 190 and 191 each having ashape of an almost rectangular parallelepiped are bonded on the lightreceiving means 91 and 92. Preferably these raised members 190 and 191are made of materials easy to handle and having a strength to someextent such as metal or resin.

With these raised members 190 and 191 being mounted, it is possible tograsp and move the raised members 190 and 191 along the substrateportion 70 a in relative positioning of the light receiving means 91 and92 to the light sources 2 and 9, and therefore fine positioning of thelight receiving means 91 and 92 can be easily performed. Accordingly, itis possible to perform relative positioning between the light source 2or 9 and the light receiving means 91 or 92 more precisely, andtherefore it is possible to suppress a degradation of signalcharacteristics caused by a deviation from a fixed position, which leadsto actualizing a high-performance and very reliable optical pickup.

In this embodiment, at least one of the raised portions 190 and 191 isused as a supporting member of the first optical member 72. Now, thispoint will be described below.

In this embodiment, at least a part of the top of the raised members 190and 191 is formed so as to have a height from the top of the substrateportion 70 a at the same level as for the optical member mounting areawhich is arranged in at least one of the light source mounting portions180 and 181 so that the first optical member 72 can be mounted thereon.In other words, the first optical member 72 is supported by at least oneof the light source mounting portions 180 and 181 and at least one ofthe raised members 190 and 191 in this configuration.

With this configuration, relative positioning between the light source 2or 9 and the light receiving means 91 or 92 can be performed moreprecisely, while an installation error of the first optical member 72,particularly a parallelism to the substrate portion 70 a can beimproved, and therefore an installation precision of the first opticalmember 72 can be further increased. Particularly, the first opticalmember 72 and the optical axis of the light emitted from the lightsource 2 or 9 can be made almost perpendicular to each other precisely,and therefore the characteristics of the light incident on the firstoptical member 72 can be favorably maintained and the light emitted fromthe first optical member 72 can be made incident in a predeterminedposition of the second optical member 86 precisely. Accordingly, it ispossible to actualize a very reliable optical pickup having favorableoptical characteristics.

Next, the light source mounting portions 180 and 181 will be explainedby using FIGS. 17 and 18. Referring to FIG. 17, there is shown aperspective view of a peripheral portion of the light source mountingportion of the third embodiment according to the present invention, andreferring to FIG. 18, there is shown a cross section of the peripheralportion of the light source mounting portion of the third embodimentaccording to the present invention.

The top of the light source mounting portion 180 on which the lightsource 2 is mounted does not exist in the same plane as for the top ofthe light source mounting portion 181 on which the light source 9 ismounted. In other words, assuming that the light source mountingportions 180 and 181 exist in the same plane on the same substrate, thelight source mounting portion 180 has a different height from that ofthe light source mounting portion 181. In this configuration, the firstoptical member 72 described later is mounted on the top of the higherlight source mounting portion.

In this embodiment, the light source mounting portion 180 and the lightsource mounting portion 181 are mounted on the same substrate portion 70a, with the light source mounting portion 181 being formed higher thanthe light source mounting portion 180 and with the first optical member72 being mounted on the top of the light source mounting portion 181,bonded each other.

With this configuration, only the top of the light source mountingportion 181 is required to be finished for bonding the first opticalmember 72, and therefore a process of surface grinding of the top of thelight source mounting portion 180 can be omitted, so as to increaseproductivity.

In addition, in comparison with a configuration in which the firstoptical member 72 is mounted on each top of the light source mountingportions 180 and 181, it is possible to decrease the possibility ofdegrading the optical characteristics.

In other words, if the first optical member 72 is mounted on both of thetops of the light source mounting portions 180 and 181, the light sourcemounting portion 180 must have accurately the same height as for thelight source mounting potion 181. If there were a minute differencebetween the height of the light source mounting portion 180 and that ofthe light source mounting portion 181, it causes a phenomenon that thefirst optical member 72 inclines at an angle according to the differenceof the heights. This inclination of the first optical member 72 causesdisadvantages, for example, that an aberration is generated in the lightincident from the light source 2 or the light source 9, that opticalcharacteristics to be originally given cannot be correctly provided, orthat the light emitted from the first optical member 72 cannot be guidedto a predetermined position.

To cope with these problems, in a configuration according to thisembodiment, a mounting area for the first optical member 72 is one ofthe tops of the plurality of light source mounting portions, andtherefore there is no inclination of the first optical member caused bya deviation of the heights between respective light source mountingportions, so that a predetermined workability of the first opticalmember 72 can be obtained by chamfering precisely the top of just one ofthe light source mounting portions. Accordingly, it is possible toachieve an optical pickup having superior performance withoutdegradation of optical characteristics in a simple configuration.

Next, an arrangement of the light source mounting portions 180 and 181on the substrate portion 70 a will be explained with reference to theaccompanying drawings.

The substrate portion 70 a has a projection 93 and further the lightsource mounting portions 180 and 181 are put on a surface 70 f of thesubstrate portion 70 a. The mounting positions of the light sourcemounting portions 180 and 181 can be determined by bringing a sideportion 93 a of the projection 93 into contact with side portions 180 aand 181 a of the light source mounting portions 180 and 181 mounted onthe surface 70 f of the substrate portion 70 a. In a lot of cases, theprojection 93 has a shape of a rectangular parallelepiped. Thisprojection 93 can be formed as a part of the substrate portion 70 a oras a member separated from the substrate portion 70 a.

Preferably, the side portion 93 a of the projection 93 has the sameangle of inclination in a contact position as for the side portions 180a and 181 a of the light source mounting portions 180 and 181 so thatthey are precisely in contact with each other. Furthermore, preferablyrespective surfaces are processed so as to have an average surfacedegree of roughness of 10 μm or lower in grinding processing or the likesince a precision of bonding between both sides can be improved.Similarly, the same processing is preferably applied to the surface 70 fof the substrate portion 70 and the bottoms 180 b and 181 b of the lightsource mounting portions 180 and 181.

By using this configuration, it becomes possible to arrange componentsmore easily and more precisely in predetermined positions of the lightsource mounting portions 180 and 181 on which the light sources 2 and 9are mounted, whereby a high-performance optical pickup can be obtainedwith less degradation of the optical characteristics caused by apositional deviation of the light source 2 or 9.

As bonding material used for bonding the light source mounting portion180 or 181 and the substrate portions 70 a, preferably a metallicbonding material such as solder or optical hardening resin which ishardened by UV light or visible light is used since each of them hasbonding power greater than a requested value so as to simplify a bondingprocess. Particularly, if a metallic bonding material is used, it ispreferable to take measures so as to have favorable bonding effects, forexample, by previously applying metallic plating to the surface 70 f ofthe substrate portion 70 a, the side 93 a of the projection 93, thebottoms 180 b and 181 b of the light source mounting portions 180 and181, and the sides 180 a and 181 a. The bonding material can be appliedonly to the side of the light source mounting portions 180 and 181 oronly to the side of the substrate portion 70 a (the projection 93), orit can be applied to both sides.

In addition, an angular portion made by the bottom 180 b or 181 b of thelight source mounting portion 180 or 181 and the side 180 a or 181 a putin contact with the projection 93 preferably has a predetermined radius(R) or has a corner whose sharp edge is removed.

By using this configuration, it becomes possible to bond the lightsource mounting portions 180 and 181 to the substrate portion 70 a inaccurate positions even if the surface 70 f of the substrate portion 70a and the side 180 a of the projection 93 do not cross at right angles,and therefore the optical pickup has favorable recording or reproductioncharacteristics without any deviation from a predetermined optical axisof the light emitted from the light source 2 or 9 which is mounted onthe light source mounting portions 180 and 181.

Furthermore, the light sources 2 and 9 mounted on the light sourcemounting portions 180 and 181 are favorably formed so as to face theprojection 93 in the same manner as for the second embodiment, in otherwords, so as to form the projection 93 in an extending direction of thebackward emitting light 2 h from the light source 2 and the backwardemitting light 9 h from the light source 9.

In this embodiment, particularly it is preferable to form the lightsource mounting portion 181 at a higher position than the height of thelight source mounting portion 180 and to put the first optical member 72on the top of the light source mounting portion 181 with bonding. Itwill now be explained below.

In this embodiment, the light source 2 mounted on the light sourcemounting portion 180 is provided for recording or reproduction of thehigh-density optical disk, and the light source 9 mounted on the lightsource mounting portion 181 is provided for reproduction of thelow-density optical disk.

Generally, a light source having a highly great output power (normally25 nw or greater output) is used in recording on an optical disk, whilereproduction on the optical disk does not need a light source havingsuch great output power, but only requiring a light source of aseveral-mw class normally. Additionally in general, heat discharged froma light source is increased as the output power is increased.

In the configuration as shown in this embodiment in which the opticalmember is put on the top of the light source mounting portion, the heatdischarged from this light source and transmitted via the light sourcemounting portion is easy to be a problem. Particularly the amount of theheat discharged from the light source 2 having a greater output isconsiderably high, and therefore there is a large difference between atemperature of the first optical member 72 at an active operation of thelight source 2 and a temperature of the first optical member 72 at aninactive operation of the light source 2, which may cause disadvantages,for example, that the first optical member 72 cannot maintain the givenoptical characteristics due to a distortion of the first optical member72 made of optical glass or that the first optical member 72 is brokensince a bonded portion cracks due to a distortion on a bonded areabetween respective prisms of the first optical member 72 made of aplurality of laminated prisms.

To cope with this problem, in this embodiment, the light source mountingportion 181 on which the light source 9 is mounted is formed in aposition higher than the light source mounting portion 180 on which thelight source 2 is mounted with the first optical member 72 mounted onthe top of the higher light source mounting portion 181 so as to preventthe heat generated by the light source 2 from being conducted to thefirst optical member 72 via the light source mounting portion 180 inorder to suppress an occurrence of the above described disadvantages.

Even if a light source having a great output power is installed in theoptical pickup, it is also effective to minimize the disadvantagescaused by effects of the heat generated by the light source, so as toactualize a high-performance and very reliable optical pickup havingstable optical characteristics.

As described above, the first optical member 72 is mounted on the top ofthe light source mounting portion 181. As bonding material used forbonding between the first optical member 72 and the light sourcemounting portion 181, it is preferable to use previously printed glassbonding material, epoxy resin, or optical hardening resin. Particularly,the optical hardening resin has favorable workability since it is nothardened until it is irradiated with light and has strong bonding power,and therefore it is optimum for bonding of the first optical member 72which requires accurate positioning. In the optical hardening resin, itis more preferable to use visible light or UV light hardening resin towhich light having high energy can be applied and which can besolidified in relatively short time since it is effective to increasethe productivity due to a reduction of the work time.

In addition, a recess portion arranged in this embodiment is describedbelow.

In an angular portion formed by the light source mounting area and thetop of the light source mounting portion 181, a recess portion 182 isformed having a function of holding bonding material which overflows thebonded area between the first optical member 72 and the light sourcemounting potion 181 at bonding.

With this recess portion 182 formed on the top of the light sourcemounting portion 181, it is possible to prevent the bonding materialwhich overflows at the bonding of the first optical member 72 to thelight source mounting potion 181 from overflowing into a light incidentarea of the first optical member 72, so as to prevent degradation of theoptical characteristics caused by an overflow of the bonding materialwhich has been a conventional problem. Accordingly, it is possible toactualize an optical pickup having favorable optical characteristics.

Furthermore, it is preferable to have a distribution that the bondingmaterial applied to the top of the light source mounting portion 181 andto the bottom of the first optical member 72 is applied less in the sideof the light source and more in the opposite side, assuming that theapplied area is divided into two portions which are both sides of therecess portion 182. The bonding in this manner is effective to apply thebonding material enough to maintain a sufficient bonding power whileminimizing the overflow of the bonding material, and therefore thereliability of the optical pickup can be enhanced in addition to theimprovement of the optical characteristics of the optical pickup.

This configuration exerts a great effect when the optical member must bearranged at a position close to the light source. In other words, asshown in this embodiment, if the light source mounting potion serves asan area in which both of the optical member and the light source aremounted, the light from the light source passes almost touching thebonded area between the light source mounting portion and the firstoptical member taking into consideration an extent of the light emittedfrom the light source since the light source is generally very thin.Therefore, such an overflow of the bonding material in this areadegrades the optical characteristics significantly.

Still further, the light which originally cannot be guided to the diskexisting outside the predetermined optical path is not reflected norscattered by the overflow of the bonding material, and therefore thisconfiguration is effective to decrease a possibility significantly thatthis kind of light is included into the predetermined optical path to bestray light.

Although the recess portion 182 has a slot almost in parallel with theside 181 c at an end to the side 181 c of the top of the light sourcemounting portion 181 in this embodiment, the angular portion made by theside 181 c and the top of the light source mounting portion 181 can becut out in a rectangular shape or be tapered.

In addition, although the recess portion is arranged in one of the lightsource mounting portions in this embodiment, it is preferable to arrangerecess portions in both of the light source mounting portions if theyhave the same height.

Next, a method of supplying power to the light sources 2 and 9 will bedescribed below.

On the surface 180 a of the light source mounting portion 180, theelectrode 94 a and the electrode 94 b are arranged apart from eachother.

The electrode 94 a is connected to a power supply terminal 70 h forsupplying power to the light source 2 in a wire bonding or other methodand also to a surface in the anode side of the light source 2 in thewire bonding or other method so as to supply power to the light source2.

In addition, the electrode 94 b is arranged apart from the electrode 94a. The light source 2 is mounted on the top of it so that the electrode94 b is in contact with the surface in the cathode side of the lightsource 2 so as to serve as a ground of the light source 2.

On the area opposing to the substrate portion 70 a of the light sourcemounting portion 180, the electrode 94 c is formed. The electrode 94 cis connected to the electrode 94 b, and the light source mountingportion 181 is put in contact with an electrode 94 d formed on thesubstrate 70 a when it is installed in the substrate portion 70 a.

In the side of the area 181 a of the light source mounting portion 181,the electrode 94 c and an electrode 94 f are formed, and further in theside of the area opposing to the substrate portion 70 a of the lightsource mounting portion 181, an electrode 94 g is formed.

An electrode 94 e is connected to a power supply terminal 70 i forsupplying power to the light source 9 in a wire bonding or other methodand also to a surface in the anode side of the light source 9 in thewire bonding or other method so as to supply power to the light source9.

In addition, the electrode 94 f is arranged apart from the electrode 94c and electrically connected with the electrode 94 g, and the lightsource 9 is mounted on it. The electrode 94 f is in contact with thesurface in the cathode side of the light source 9 so as to serve as aground of the light source 9.

On the area opposing to the substrate portion 70 a of the light sourcemounting portion 181, the electrode 94 h is formed. The electrode 94 his connected to the electrode 94 g, and the light source mountingportion 181 is put in contact with an electrode 94 d formed on thesubstrate 70 a when it is installed in the substrate portion 70 a.

The electrode 94 d can be monolithically integrated with the electrode94 h.

Then, how to ground the optical pickup will be explained below. In thisembodiment, the substrate portion 70 a is made of a metallic, resin,ceramic or other insulating material, having a shape of a plate.Particularly, the metallic or ceramic material is preferable since theyhave favorable heat dissipation characteristics so as to dissipate theheat transmitted from the light sources efficiently.

Now an embodiment will be described below in which the substrate portion70 a is made of an insulating material. In this embodiment, thesubstrate portion 70 a has a hole through which the terminal 70 c passesto be arranged and the electrode 94 i to be a ground for the lightsources 2 and 9. This electrode 94 i is electrically connected to theelectrode 94 d and 94 h. Then, the electrode 94 i passes from thesurface (front) in the side of the area in which the light sourcemounting portion of the substrate portion 70 a is mounted, through theside of the substrate portion 70 a, to the surface (bottom) in theopposite side of the area in which the light source mounting portion ofthe substrate portion 70 a is mounted, and is connected to a groundterminal 70 j at the bottom.

Although the light sources 2 and 9 are connected to the ground terminal70 j via the electrode 94 d which passes around the substrate portion 70a in this embodiment, a hole for the ground terminal 70 j may bearranged on the substrate portion 70 a in the same manner as for thesecond embodiment, so that the ground terminal 70 j passes through thesubstrate portion 70 a and then the terminal passing through the holemay be connected to the electrode mounted on the substrate portion orthe light source mounting portion in a wire bonding or soldering method.

If the substrate portion 70 a is made of a metallic material, with theentire substrate portion 70 a used as a ground, the ground terminal 70 jconnected to the bottom of the substrate portion 70 a may be connectedto the electrode 94 i of the substrate portion 70 a via the substrateportion 70 a.

In either case, the ground terminal 70 j is arranged in the front of thesubstrate portion 70 a through the hole, and it may be electricallyconnected with the electrode 94 i.

As described above, with electrodes for a ground of the plurality oflight sources arranged in common, only one ground terminal 70 j isrequired so as to decrease the number of the terminals. It is effectiveto relieve the problems such as an increase of the number of terminalswhich has conventionally occurred in the optical head containing aplurality of light sources in a single package and restrictions on anarrangement of terminals in a package substrate, so as to increase adegree of freedom in designing an optical head in which a plurality oflight sources are arranged in a single package.

Further, if a single light source mounting portion corresponds to asingle light source with each electrode for a ground arranged in thelight source mounting portions individually as described in thisembodiment, this configuration is favorable since ground terminals neednot be arranged for respective ground electrodes separated from eachother, in other words, by the number of the light source mountingportions, whereby the number of the ground terminals can be decreasedeffectively.

Still further, with the configuration in which the light sources 2 and 9directly are put on the electrodes and the electrodes are in contactwith the ground terminal, it does not need to have a process ofconnecting the electrodes to the light sources by means of connectionmeans for wire bonding, and therefore the number of manufacturingprocesses of the optical head can be decreased so as to improve theproductivity of the optical head.

Next, it is preferable to seal the inside space enclosed by the package70, in other words, the space in which the light sources 2 and 9 and thelight receiving means are arranged. This configuration is effective toprevent impurities such as dust or moisture from being included into theinside of the package, whereby the performances of the light sources 2and 9 and the light receiving means can be maintained and it is possibleto prevent a degradation of the optical characteristics of the emittedlight.

In this embodiment, the package 70 is sealed by the second opticalmember 86. In other words, the bottom of the first substrate 86 a of thesecond optical member 86 is bonded to the outer surface of the sidewallportion 70 b of the package 70 so as to close the opening 70 d arrangedon the package 70. As bonding materials for this connection, opticalhardening resin, epoxy resin, or bonding glass is often used.

It is preferable to enclose an inactive gas such as N2 gas, a dry air,or Ar gas in the sealed space since it is effective to prevent adegradation of various optical characteristics caused by moisturecondensation on the surfaces of the first optical member 72 in thepackage 70 or a degradation of the characteristics caused by anoxidation of the light sources or the light receiving means.

Similarly, the configuration, in which the second optical member isbonded to the sidewall portion 70 b of the package 70 by using thebonding material so as to seal the package 70, does not need a coverglass which has been conventionally used only in order to close thisportion and it can be omitted here, and therefore the configuration ofthe optical pickup can be simplified so as to decrease the number ofcomponents. In addition, although the manufacturing of an optical pickupconventionally requires two processes in total, a process in whichoptical members are bonded with positioning and a process in which acover member for closing a package is bonded, it is possible to reducethe manufacturing processes of the optical pickup from the above twoprocesses to the former single process, and therefore the manufacturingprocess of the optical pickup can be simplified so as to increase theproductivity of the optical pickup.

In addition, since the second optical member 86 is exposed to theoutside of the package 70, the package can be downsized in comparisonwith a configuration in which it is contained in the package and thenumber of the inclined planes in the optical member can be significantlydecreased in comparison with a configuration in which required opticalelements are formed in a single optical member, and therefore the sizeof the optical pickup can be significantly reduced particularly in thewidth direction, whereby it is possible to further downsize an opticalpickup so as to increase an efficiency of utilizing a space of theoptical pickup.

Furthermore, almost all of the required optical systems are mounted in asingle head with the optical member separated into two parts, wherebythe pickup assembly process can be significantly simplified so as toachieve a user-friendly optical pickup.

In the second optical member 86, there is not arranged any opticalelements in an area exposed to the outside, and therefore it is possibleto prevent an occurrence of disadvantages, for example, that givenperformances cannot be maintained since the optical elements are exposedto the surrounding air and absorbs moisture or that the characteristicsare degraded due to dust on the optical elements.

At this point, the inside pressure of the package 70 is preferablynegative. It is effective to make the bonding effects favorable betweenthe second optical member 86 and the package 70 since a force is appliedin a direction in which the second optical member 86 bonded to thesidewall portion 70 b of the package 70 is pulled from the outside ofthe package toward the inside of the package 70.

Next, an embodiment having further favorable configuration will bedescribed.

In this configuration, the package 70 is not closed only by the secondoptical member 86 from the outside, but the shield member 86 and thesecond optical member 86 are used to close the opening 70 d of thepackage 70. In other words, the shield member 85 is put so as to closethe opening 70 d on the sidewall portion 70 b of the package 70 from theinside of the package 70, and the second optical member 86 is put so asto close the opening 70 d on the sidewall portion 70 b of the package 70from the outside of the package 70, so as to seal the inside space ofthe package 70 by using these two members.

Advantages of this configuration will be explained below. The shieldmember 85 bonded from the inside is pressed to the sidewall portion 70 bincluding the bonding material if the inside pressure of the package 70is positive, and therefore it is possible to decrease a possibility thata leak will occur. If the inside pressure of the package 70 is negative,however, a pressure is applied in such a direction that the shieldmember is distant from the sidewall portion 70 b, and therefore itincreases a possibility that a leak will occur due to defective bonding.

To the contrary, the second optical member 86 bonded from the outside ispressed to the sidewall portion 70 b including the bonding material ifthe inside pressure of the package 70 is negative as opposite to theshield member 85, which is effective to decrease a possibility that aleak will occur, but if the inside pressure of the package 70 ispositive, the pressure is applied in such a direction that the secondoptical member 86 is distant from the sidewall portion 70 b, whichincreases a possibility that a leak will occur due to defective bonding.

In other words, with the shield member 85 and the second optical member86 arranged so that the sidewall portion 70 b of the package 70 is putbetween them, a pressure is applied in such a direction that at leastone of the shield member 85 and the second optical member 86 is pressedto the sidewall portion 70 b whether the inside pressure of the package70 is positive or negative, and therefore it becomes possible to reduceoccurrences of a leak caused by a difference of atmospheric pressure ordefective bonding.

With this configuration, the air-tightness of the inside of the package70 can be improved, whereby it becomes possible to prevent an occurrenceof disadvantages caused by a condition that any of the light sources,the light receiving elements, or the optical members arranged inside thepackage 70 is put in contact with the air or includes moisture, whichleads to achieving a very reliable optical pickup.

For the material of the shield member 85, it is preferable to use amaterial having favorable transparency such as resin or glass which doesnot decrease an efficiency of utilizing light. In addition, a thinnershield member is preferable to an extent that it does not cause anyproblem of its strength since it is effective to minimize an expansionof a diameter of the light.

Furthermore, the bonding power of the shield member 85 to the sidewallportion 70 b is preferably different from that of the second opticalmember 86 to the sidewall portion 70 b. Particularly, with the bondingpower of the shield member 85 directly facing the inside of the package70 to the sidewall portion being greater than that of the second opticalmember 86, a leak between the second optical member 86 and the sidewallportion 70 b is inhibited to reach the inside of the package 70 even ifsuch a leak may occur. It is effective to largely decrease a possibilityof an occurrence of a leak into the inside of the package 70. As a meansfor realizing this configuration, there may be provided a method ofusing a bonding material having a greater bonding power for the bondingbetween the shield member 85 and the sidewall portion 70 b in comparisonwith that of the bonding material used for the bonding between thesecond optical member 86 and the sidewall portion 70 b.

Still further, preferably a difference of a pressure is as small aspossible between a space A enclosed by the package 70 and the shieldmember 85 and a space B enclosed by the sidewall portion 70 b, theshield member 85, and the second optical member 86. A pressure is alwaysapplied to the shield member 85 between the space A and the space B dueto a difference of a pressure between the space A and the space B. If avibration caused by hand carriage or car mounting of the product isentered into the shield member 85 in this condition, the shield member85 significantly vibrates or is deflected and it may change minutely anangle of incidence formed by an incident light and the shield member 85,and it may further lead to a degradation of optical characteristics.Additionally, the difference of the pressures may cause deformation ofthe shield member 85, by which an aberration will be generated so as todegrade the optical characteristics.

From this viewpoint, the difference of the pressure (P) is preferably assmall as possible between the space A and the space B. In thisembodiment, unlike the first embodiment, specifically P is preferably0.25 (atm) or lower since the opening is relatively large out ofnecessity for a plurality of optical paths in the opening.

In this manner, it is possible to prevent a degradation of the opticalcharacteristics caused by a difference of the pressure between the spaceA and the space B.

Next, an operation of the optical pickup having these configurationswill be explained.

If the record medium is the high-density optical disk 18, light isemitted from the light source 2 for recording or reproducinginformation. In this case, the light emitted from the light source 2 isfirst reflected by the reflection film 73 formed on the first inclinedplane 72 a on the first optical member 72 and then incident on thepolarizing separation film 75 formed on the second inclined plane 72 b.This polarizing separation film 75 reflects a linear polarizationemitted from the light source 2 and transmits light in a polarizationdirection which crosses at right angles with it, and therefore the lightemitted from the light source 2 is reflected.

Afterward, the light emitted from the first optical member 72 istransmitted through the shield member 85, transmitted through the firstsubstrate 86 a of the second optical member 86, and further transmittedthrough the filter 89 formed on the second inclined plane 86 e of thesecond substrate 86 b of the second optical member 86, and then emittedfrom the second optical member 86 and incident on the quarter-wavelengthplate 90. The light incident on the quarter-wavelength plate 90 isconverted from the linear polarization to an elliptic polarization inits polarization direction and then emitted from the quarter-wavelengthplate 90.

Afterward, if there is a collimator lens, the light emitted from thelight source 2 passes through the collimator lens 16 and is converted toalmost parallel light before it is incident on the condenser 17, andotherwise, it is directly incident on the condenser 17, and then thelight is converged to the high-density optical disk 18.

Returning light which has been reflected by the high-density opticaldisk 18 is incident on the quarter-wavelength plate 90 again. This lighthas a rotational direction of the elliptic polarization which isopposite to that of the incidence when it is reflected by thehigh-density optical disk 18, and therefore when passing through thequarter-wavelength plate 90, it is converted from the ellipticpolarization to the linear polarization which crosses at almost rightangles with the polarization direction of the light emitted from thelight source 2. In other words, assuming that the light is emitted fromthe light source 2 in an S polarization, it is incident on the opticalmember in a P polarization.

The light which has passed through the quarter-wavelength plate 90 isincident on the second optical member 86, transmitted through the filter89 on the second inclined plane 86 e of the second substrate 86 b almostcompletely, emitted from the second optical member 86, furthertransmitted through the shield member 85, and incident on the firstoptical member 72.

Then the light is incident on the polarizing separation film 75 on thesecond inclined plane 72 b of the first optical member 72. The incidentlight is directed so as to cross at right angles with the emitted lightin its polarization direction, and therefore the light is transmittedthrough the polarizing separation film 75 almost completely and thenincident on the optical path dividing means 83 on the third inclinedplane 72 c of the first optical member 72. This optical path dividingmeans 83 transmits almost a half of the incident light and reflectsanother half of the incident light.

After that, the light transmitted by the optical path dividing means 83is directly formed in a luminous flux having a predetermined shape inthe light receiving portion arranged in a predetermined position of thelight receiving means 91 under the first optical member 72, so as to beprovided for generating signals according to purposes.

The light reflected by the optical path dividing means 83 is reflectedby the reflection film 81 on the second inclined plane 72 b of the firstoptical member 72 and then formed in luminous flux having apredetermined shape in the predetermined light receiving portion in thelight receiving means 91, so as to be provided for generating signalsaccording to purposes.

If the record medium is the low-density optical disk 19, light isemitted from the light source 9 for recording or reproducinginformation. In this case, the light emitted from the light source 9 isfirst reflected by the reflection film 74 formed on the first inclinedplane 72 a of the first optical member 72 and then incident on thepolarizing separation film 76 formed on the second inclined plane 72 b.This polarizing separation film 76 reflects a linear polarizationemitted from the light source 9 and transmits light in a polarizationdirection which crosses at right angles with it, and therefore the lightemitted from the light source 9 is reflected.

Afterward, the light emitted from the first optical member 72 isincident on the diffusion angle converting means 87 which is formed onthe lower end surface of the first substrate 86 a of the second opticalmember 86. By this diffusion angle converting means 87, the diffusionangle of the light emitted from the light source 9 is converted so thatthe diffused light is converted to converged light and then emitted fromthe second substrate 86 b, further the light is incident on the meansfor forming a plurality of beams 88 on the first inclined plane 86 d ofthe second substrate 86 b of the second optical member 86, transmittedthrough the polarizing separation film 88 a, separated to a single mainbeam and two side beams when being reflected by the beam separatingportion 88 b, and then incident on the filter 89 on the second inclinedplane 86 e. This filter 89 has functions to reflect light emitted fromthe light source 9 and to transmit light emitted from the light source2, and therefore the light incident on the filter 89 from the means forforming a plurality of beams 88 is reflected almost completely and thenemitted from the second optical member 86.

Afterward, the light emitted from the light source 9 is incident on thequarter-wavelength plate 90. The light incident on thequarter-wavelength plate 90 is converted from the linear polarization toan elliptic polarization in its polarization direction and then emittedfrom the quarter-wavelength plate 90.

Subsequently, if there is a collimator lens, the light emitted from thelight source 9 passes through the collimater lens 16 and is converted tolight having a smaller diffusion angle before it is incident on thecondenser 17, and otherwise, it is directly incident on the condenser17, and then the light is converged to the high-density optical disk 18.

Returning light which has been reflected by the low-density optical disk19 is incident on the quarter-wavelength plate 90 again. This light hasa rotational direction of the elliptic polarization which is opposite tothat of the incidence when it is reflected by the low-density opticaldisk 19, and therefore when passing through the quarter-wavelength plate90, it is converted from the elliptic polarization to the linearpolarization which crosses at almost right angles with the polarizationdirection of the light emitted from the light source 9. In other words,assuming that the light is emitted from the light source 9 in an Spolarization, it is incident on the optical member in a P polarization.

The light which has passed through the quarter-wavelength plate 90 isincident on the second optical member 86, reflected by the filter 89 onthe second inclined plane 86 e of the second substrate 86 b almostcompletely, and then incident on the means for forming a plurality ofbeams 88 on the first inclined plane 86 d. In this case, the incidentlight is directed so as to cross at almost right angles with the emittedlight in its polarization direction, and therefore the incident light isreflected by the polarizing separation film 88 a without being incidenton the beam separating portion 88 b almost at all, emitted from thesecond substrate 86 b, and then incident on the diffusion angleconverting means 87 on the first substrate 86 a.

The light incident as a diffused light on the diffusion angle convertingmeans 87 is converted to converged light with a conversion of thediffusion angle, and then emitted from the second optical member 86,further transmitted through the shield member 85, and then incident onthe first optical member 72.

Then the light is incident on the polarizing separation film 76 on thesecond inclined plane 72 b of the first optical member 72. The incidentlight is directed so as to cross at right angles with the emitted lightin its polarization direction, and therefore the light is transmittedthrough the polarizing separation film 76 almost completely and thenincident on the optical path dividing means 84 on the third inclinedplane 72 c. This optical path dividing means 84 transmits almost half ofthe incident light and reflects another half of the incident light.

After that, the light transmitted by the optical path dividing means 84is directly formed into a luminous flux having a predetermined shape inthe light receiving portion arranged in a predetermined position of thelight receiving means 92 under the fourth optical member, so as to beprovided for generating signals according to purposes.

The light reflected by the optical path dividing means 84 is reflectedby the reflection film 82 on the second inclined plane 72 b and thenformed into luminous flux having a predetermined shape in thepredetermined light receiving portion in the light receiving means 92,so as to be provided for generating signals according to purposes.

As set forth hereinabove, also when a plurality of light sources arearranged in an identical package, the light emitted from respectivelight sources has a great wavefront aberration in the same manner as forthe second embodiment in many cases, and accordingly an optimization isperformed for a distance between the luminous point 2 a or 9 a of thelight source 2 or 9 and the lens. The concept is, however, the same asfor the second embodiment, and therefore the explanation is omittedhere.

What is claimed is:
 1. An optical pickup device for recordinginformation onto and/or reading out information from an opticalrecording medium that is positioned at a recording medium positioningarea of an optical recording and/or reproducing apparatus, said devicecomprising: a first light beam source for emitting a first light beam toimpinge upon and be reflected by a recording medium positioned at therecording medium positioning area, a second light beam source foremitting a second light beam to impinge upon and be reflected by arecording medium positioned at the recording medium positioning area, alight beam detector for receiving at least one of the first and secondlight beams after being reflected by a recording medium at the recordingmedium positioning area so that the information is read from the atleast one of the first and second light beams after being reflected, alight beam diameter changing rate adjusting member to adjust a changingrate of a diameter of either of the first and second light beams,wherein the light beam diameter changing rate adjusting member has anexposed surface through which the either of the first and second lightbeams passes, and a refractive index of a substance contacting theexposed surface is smaller than that of the light beam diameter changingrate adjusting member.
 2. An optical pickup device according to claim 1,wherein a difference in refractive index between the substance and thelight beam diameter changing rate adjusting member is not less than 0.35to 0.5.
 3. An optical pickup device according to claim 1, wherein saidoptical pickup device further comprises an objective element forcondensing the first and second light beams at separate times.
 4. Anoptical pickup device for recording information onto and/or reading outinformation from an optical recording medium that is positioned at arecording medium positioning area of an optical recording and/orreproducing apparatus, said device comprising: a first light beam sourcefor emitting a first light beam to impinge upon and be reflected by arecording medium positioned at the recording medium positioning area, asecond light beam source for emitting a second light beam to impingeupon and be reflected by a recording medium positioned at the recordingmedium positioning area, a light beam detector for receiving at leastone of the first and second light beams after being reflected by arecording medium at the recording medium positioning area so that theinformation is read from the at least one of the first and second lightbeams after being reflected, a container housing therein the first andsecond light beam sources and the light beam detector and including anaperture through which the first and second light beams proceed atseparate times, and a light beam guide member mounted on an outersurface of the container and covering the aperture to guide the firstand second light beams such that the first and second light beamsproceed, at separate times, toward the recording medium positioning areaand the at least one of the first and second light beams, after beingreflected, is received by the light beam detector.
 5. An optical pickupdevice according to claim 4, wherein the container is hermeticallysealed by the light beam guide member.
 6. An optical pickup deviceaccording to claim 2, further comprising an electrically grounded memberto which both of the first and second light sources are electricallyconnected.
 7. An optical pickup device according to claim 6, wherein theelectrically grounded member is mounted on the container.
 8. An opticalpickup device according to claim 2, wherein the light beam detectordetects either of the first and second light beams on a common plane. 9.An optical pickup device according to claim 8, wherein a position on thecommon plane detecting the first light beam is different from anotherposition on the common plane detecting the second light beam.
 10. Anoptical pickup device according to claim 8, wherein the common plane isarranged in the container.
 11. An optical pickup device according toclaim 2, further comprising a first light beam source base on which thefirst light beam source is mounted, and a second light beam source baseon which the second light beam source is mounted, wherein a power of thefirst light beam is larger than that of the second light beam, and aheat energy absorption value of the first light beam source base islarger than that of the second light beam source base.
 12. An opticalpickup device according to claim 11, wherein a volume of the first lightbeam source base is larger than that of the second light beam sourcebase.
 13. An optical pickup device according to claim 11, wherein asurface area of the first light beam source base is larger than that ofthe second light beam source base.
 14. An optical pickup deviceaccording to claim 11, wherein a heat energy transmission rate from thefirst light beam source base is larger than a heat energy transmissionrate from the second light beam source base.
 15. An optical pickupdevice according to claim 11, wherein a radiant heat energy rate fromthe first light beam source base is larger than a radiant heat energyrate from the second light beam source base.
 16. An optical pickupdevice according to claim 2, further comprising a first light beamsource base on which the first light beam source is mounted, and asecond light beam source base on which the second light beam source ismounted, wherein a power of the first light beam is larger than that ofthe second light beam, and a distance is formed at least partiallybetween surfaces of the first and second light beam source bases opposedto each other.
 17. An optical pickup device according to claim 16,wherein a contact area is formed partially between the surfaces of thefirst and second light beam source bases opposed to each other.
 18. Anoptical pickup device according to claim 2, further comprising anobjective for focusing either of the first and second light beams, and achromatic aberration compensating member arranged between at least oneof the first and second light beam sources and the objective to performa chromatic aberration compensation for the light beam from the at leastone of the first and second light beam sources.
 19. An optical pickupdevice according to claim 18, wherein the chromatic aberrationcompensating member is a hologram.
 20. An optical pickup deviceaccording to claim 18, wherein the chromatic aberration compensatingmember arranged between one of the first and second light beam sourcesand the objective.
 21. An optical pickup device according to claim 18,wherein a chromatic aberration compensating degree for the first lightbeam is different from a chromatic aberration compensating degree forthe second light beam.
 22. An optical pickup device according to claim4, further comprising an objective element for focusing the light beamson the recording medium positioning area, and a chromatic aberrationcompensating member arranged between the light sources and the objectiveelement to perform a chromatic aberration compensation for the lightbeams from the light sources.
 23. An optical pickup device according toclaim 4, wherein said optical pickup device further comprises anobjective element for condensing the first and second light beams atseparate times.
 24. An optical pickup device for recording informationonto and/or reading out information from an optical recording mediumthat is positioned at a recording medium positioning area of an opticalrecording and/or reproducing apparatus, said device comprising: a firstlight beam source for emitting a first light beam to impinge upon and bereflected by a recording medium positioned at the recording mediumpositioning area, a second light beam source for emitting a second lightbeam to impinge upon and be reflected by a recording medium positionedat the recording medium positioning area, a light beam detector forreceiving at least one of the first and second light beams after beingreflected by a recording medium at the recording medium positioning areaso that the information is read from the at least one of the first andsecond light beams after being reflected, a first light beam source baseon which the first light beam source is mounted, a second light beamsource base on which the second light beam source is mounted, and anoptical treating member for receiving either of the first and secondlight beams so that at least one of a light beam diameter, a proceedingcourse, a light beam diameter changing rate, a polarization and achromatic aberration of the either of the first and second light beamsis changed, and the optical treating member is mounting on one of thefirst and second light beam source bases and is prevented from beingsupported on another one of the first and second light beam sourcebases.
 25. An optical pickup device according to claim 24, wherein saidoptical pickup device further comprises an objective element forcondensing the first and second light beams at separate times.
 26. Anoptical pickup device for recording information onto and/or reading outinformation from an optical recording medium, said device comprising: alight beam source for emitting a light beam for impinging upon and beingreflected by an optical recording medium, a light beam detector forreceiving the light beam after being reflected by the recording mediumso that the information is read from the light beam after beingreflected, a container housing therein the light beam source and thelight beam detector and including an aperture through which the lightbeam proceeds toward the recording medium and proceeds to the light beamdetector after being reflected by the recording medium, and a light beamguide member mounted on an outer surface of the container and coveringthe aperture to guide the light beam in such a manner that the lightbeam proceeds toward the recording medium and is received by the lightbeam detector after being reflected by the recording medium, wherein thelight beam guide member includes an inclined surface and an opticalelement positioned on the inclined surface to change a proceedingdirection of the light beam.
 27. An optical pickup device according toclaim 26, further comprising a shield member arranged on the containerand covering the aperture at an opposite side to the light beam guidemember.
 28. An optical pickup device according to claim 27, wherein adifference between a gaseous pressure in the aperture and a gaseouspressure surrounding the light beam source and the light beam detectoris not more than 0.3 atm.
 29. An optical pickup device according toclaim 26, further comprising an objective element for focusing the lightbeam on the recording medium, and a chromatic aberration compensatingmember arranged between the light source and the objective element toperform a chromatic aberration compensation for the light beam from thelight source.
 30. An optical pickup device for recording informationonto and/or reading out information from an optical recording mediumthat is positioned at a recording medium positioning area of an opticalrecording and/or reproducing apparatus, said device comprising: a firstlight beam source for emitting a first light beam to impinge upon and bereflected by a recording medium positioned at the recording mediumpositioning area, a second light beam source for emitting a second lightbeam to impinge upon and be reflected by a recording medium positionedat the recording medium positioning area, a light beam detector forreceiving at least one of the first and second light beams after beingreflected by a recording medium at the recording medium positioning areaso that the information is read from the at least one of the first andsecond light beams after being reflected, a first light beam source baseon which the first light beam source is mounted, a second light beamsource base on which the second light beam source is mounted, and anoptical treating member for receiving either of the first and secondlight beams so that at least one of a light beam diameter, a proceedingcourse, a light beam diameter changing rate, a polarization and achromatic aberration of the either of the first and second light beamsis changed, a power of the first light beam is larger than that of thesecond light beam, wherein the optical treating member is mounted on thesecond light beam source base.
 31. An optical pickup device according toclaim 30, wherein the optical treating member is prevented from beingsupported on the first light beam source base.
 32. An optical pickupdevice according to claim 30, wherein said optical pickup device furthercomprises an objective element for condensing the first and second lightbeams at separate times.
 33. An optical pickup device for recordinginformation onto and/or reading out information from an opticalrecording medium, said device comprising: a light beam source foremitting a first light beam to impinge upon and be reflected by theoptical recording medium, a light beam source base on which the lightbeam source is mounted, a light beam detector arranged to receive thelight beam after being reflected by the recording medium so that theinformation is read from the light beam after being reflected, and alight beam guide member for guiding the light beam in such a manner thatthe light beam proceeds toward the recording medium and is received bythe light beam detector after being reflected by the recording medium,wherein the light beam guide member and the light beam source base haverespective contact surfaces through which the light beam guide memberand the light beam source base are fixed to each other, the contactsurface of at least one of the light beam guide member and the lightbeam source base is divided into at least two contact surface areas, andthe at least one of the light beam guide member and the light beamsource base has a recess between said at least two contact surfaceareas.
 34. An optical pickup device according to claim 33, the lightbeam source has the recess.
 35. An optical pickup device for recordinginformation onto and/or reading out information from an opticalrecording medium that is positioned at a recording medium positioningarea of an optical recording and/or reproducing apparatus, said devicecomprising: a first light beam source for emitting a first light beam toimpinge upon and be reflected by an optical recording medium positionedat the recording medium positioning area, a second light beam source foremitting a second light beam to impinge upon and be reflected by anoptical recording medium positioned at the recording medium positioningarea, a light beam detector for receiving at least one of the first andsecond light beams after being reflected by the optical recording mediumat the recording medium positioning area so that the information is readfrom the at least one of the first and second light beams after beingreflected by the optical recording medium, a container housing the firstand second light beam sources and the light beam detector and includingan aperture through which the first and second light beams proceed, atseparate times, toward the optical recording medium and to the lightbeam detector after being reflected by the optical recording medium, anda light beam guide member (i) including an inclined surface and anoptical element disposed on the inclined surface to change a proceedingdirection of either of the first and second light beams, (ii) mountedonto an outer surface of the container, and (ii) covering the apertureto guide the first and second light beams, in such a manner that theeither of the first and second light beams proceed, at separate times,toward the optical recording medium and the at least one of the firstand second light beams after being reflected by the optical recordingmedium is received by the light beam detector.
 36. An optical pickupdevice according to claim 35, further comprising an objective elementdisposed between the light beam guide member and the recording mediumpositioning area to focus the either of the first and second lightbeams.
 37. An optical pickup device according to claim 35, furthercomprising an objective element for focusing the light beams on therecording medium positioning area, and a chromatic aberrationcompensating member arranged between the light sources and the objectiveelement to perform a chromatic aberration compensation for the lightbeams from the light sources.
 38. An optical pickup device according toclaim 35, wherein said optical pickup device further comprises anobjective element for condensing the first and second light beams atseparate times.
 39. An optical pickup device for recording informationonto and/or reading out information from an optical recording mediumthat is positioned at a recording medium positioning area of an opticalrecording and/or reproducing apparatus, said device comprising: a firstlight beam source for emitting a first light beam to impinge upon and bereflected by the optical recording medium, and a second light beamsource for emitting a second light beam to impinge upon and be reflectedby the recording medium, an objective element for focusing the first andsecond light beams on the recording medium, and a ratio of (i) a lengthalong a light beam axis of the second light beam between the secondlight beam source and the objective and (ii) a length along a light beamaxis of the first light beam between the first light beam source and theobjective is between 0.50 and 0.75.
 40. An optical pickup deviceaccording to claim 39, wherein a wavelength of the second light beam islonger than that of the first light beam.
 41. An optical pickup deviceaccording to claim 39, further comprising a chromatic aberrationcompensating member arranged between at least one of the first andsecond light beam sources and the objective to perform a chromaticaberration compensation for the light beam from the at least one of thefirst and second light beam sources.
 42. An optical pickup deviceaccording to claim 39, further comprising a light beam guide arrangedbetween at least one of the first and second light beam sources and theobjective to receive at least one of the first and second light beams sothat the light beam guide guides the at least one of the first andsecond light beams in such a manner that either of the first and secondlight beams proceeds along a substantially-common-single light beam axisextending toward the recording medium positioning area.
 43. An opticalpickup device according to claim 39, wherein the first light beamproceeds substantially straight from the first light beam source to theobjective element, and the second light beam is bent at least oncebetween the first light beam source and the objective element.
 44. Anoptical pickup device for recording information onto and/or reading outinformation from an optical recording medium that is positioned at arecording medium positioning area of an optical recording and/orreproducing apparatus, said device comprising: a first light beam sourcefor emitting a first light beam to impinge upon and be reflected by theoptical recording medium, and a second light beam source for emitting asecond light beam to impinge upon and be reflected by the recordingmedium, wherein the optical pickup device further comprises a collimatorelement for forming parallel rays of the first and second light beams,and a ratio of (i) a length along a light beam axis of the second lightbeam between the second light beam source and the collimator element and(ii) a length along a light beam axis of the first light beam betweenthe first light beam source and the collimator element is between 0.50and 0.75.
 45. An optical pickup device according to claim 44, wherein awavelength of the second light beam is longer than that of the firstlight beam.
 46. An optical pickup device according to claim 44, furthercomprising a chromatic aberration compensating member arranged betweenat least one of the first and second light beam sources and thecollimator element to perform a chromatic aberration compensation forthe light beam from the at least one of the first and second light beamsources.
 47. An optical pickup device according to claim 44, furthercomprising a light beam guide arranged between at least one of the firstand second light beam sources and the collimator element to receive atleast one of the first and second light beams so that the light beamguide guides the at least one of the first and second light beams insuch a manner that either of the first and second light beams proceedsalong a substantially-common-single light beam axis extending toward therecording medium positioning area.
 48. An optical pickup deviceaccording to claim 44, wherein the first light beam proceedssubstantially straight from the first light beam source to thecollimator element, and the second light beam is bent at least oncebetween the first light beam source and the collimator element.